Method for transmitting control information and base station, and method for receiving control information and user equipment

ABSTRACT

According to one aspect of the present invention, antennas or antenna nodes spaced away from each other by a predetermined distance or more are configured to be able to transmit control information of mutually different user equipment groups, thereby increasing the efficiency in the operation of control channels. In addition, according to another aspect of the present invention, a resource region for transmitting control information for an improved user equipment, which is a target of a multi-node cooperative transmission, is set differently from a resource region for transmitting control information for a legacy user equipment, thereby increasing the efficiency in the transmission of the control information for the improved user equipment.

TECHNICAL FIELD

The present invention relates to a wireless communication system. Morespecifically, the present invention relates to a method of transmittingcontrol information regarding a user equipment in a multi-node systemsupporting multi-node coordinated transmission and a base stationthereof, and a method of the user equipment receiving the controlinformation and the user equipment.

BACKGROUND ART

With development of the information industry, a technology that iscapable of transmitting various large amounts of data at high speed hasbeen required. To this end, research has been conducted into amulti-node or multi-cell coordinated transmission method thatsimultaneously performs communication at multiple nodes using the sameresource. In the multi-node or multi-cell coordinated transmissionmethod, the respective nodes perform coordinated transmission, therebyproviding higher performance than when signals are transmitted withoutcoordination.

A multi-node system supporting multi-node coordinated communication usesa plurality of nodes, each of which operates as a base station, anaccess point, an antenna, an antenna group, or a radio remote header(RRH). The nodes may be managed by a base station or a base stationcontroller which controls operations of the nodes or performsscheduling. In the multi-node system, distributed nodes are connected toa base station or a base station controller, which manages a pluralityof nodes spaced apart from each other by a predetermined distance ormore in a cell, through a cable or a dedicated line. The multi-nodesystem may be considered as a kind of Multiple Input Multiple Output(MIMO) system in that distributed nodes can support a single userequipment or multiple user equipments by simultaneously transmitting andreceiving different data streams. In terms of the MIMO system, themulti-node system transmits signals using nodes distributed at variouspositions. Consequently, a transmission area covered by each antenna isreduced as compared with a centralized antenna system (CAS), andtherefore, transmit power can be reduced. In addition, the transmissiondistance between an antenna and a user equipment is reduced, resultingin a decrease in path loss and enabling data transmission at high speed.This can improve transmission capacity and power efficiency of acellular system and satisfy communication performance of relativelyuniform quality regardless of user locations in a cell. Furthermore, abase station(s) or a base station controller(s) connected to a pluralityof distributed nodes cooperate with each other in the multi-node system,and therefore, signal loss is reduced, and correlation and interferencebetween antennas and reduced. According to the multi-node coordinatedtransmission method, therefore, it is possible to obtain a high signalto interference-plus-noise ratio (SINR).

Consequently, the multi-node coordinated transmission method may be usedwith or replace the conventional centralized antenna system (CAS) tobecome a new foundation of cellular communications in order to reducebase station installation cost and backhaul network maintenance costand, at the same time, to extend service coverage and to improve channelcapacity and SINR in a next-generation mobile communication system.

In terms of a standard, MIMO transmission must also be achieved in amulti-node system in order to secure high data capacity required bycurrent and future communication standards. Actually, IEEE 802 and 3GPP,two large standardization organizations, are essentially consideringMIMO transmission in a process of discussing a communication standardtechnology. However, the current communication standards have beendesigned in consideration of only a CAS. As a result, it is difficult toapply an advanced technology, such as an MIMO technology, to themulti-node system. For development of a future communication system,therefore, it is necessary to establish a communication standardsupporting the multi-node system.

DISCLOSURE Technical Problem

The present invention provides a method of efficiently transmittingcontrol information in a multi-node system.

Also, the present invention provides a method of providing informationindicating a node used to transmit control information or data of a userequipment, which is one of a plurality of nodes of a multi-node system,to the user equipment.

Also, the present invention provides a method of efficientlytransmitting control information regarding an improved user equipmentmanufactured according to a communication standard of a multi-nodesystem in a situation in which the improved user equipment and a legacyuser equipment manufactured according to a communication standard whichdoes not support multi-node coordinated transmission coexist.

Technical Solution

The present invention relates to a wireless communication system.Particularly in a multi-node system supporting wireless communicationthrough a plurality of nodes, control information or data transmittedfor each antenna or each antenna node are differently set to efficientlyuse a wireless resource. According to the present invention, controlinformation received by user equipments may be different from each othereven if the user equipments belong to the same cell.

Also, according to the present invention, in a situation in which animproved user equipment manufactured according to a communicationstandard of a multi-node system and a legacy user equipment manufacturedaccording to a communication standard which does not support multi-nodecoordinated transmission coexist, a region to which control informationregarding the legacy user equipment and a region to which controlinformation regarding the improved user equipment are differently set,and therefore, it is possible to efficiently transmitting controlinformation regarding the improved user equipment.

In accordance with one aspect of the present invention, there isprovided a method of transmitting control information at a base stationin a distributed antenna system including a plurality of distributedantennas spaced apart from each other by a predetermined distance ormore. The method comprises: transmitting first control informationregarding one or more legacy user equipments supporting communicationaccording to a centralized antenna system on a first resource region andtransmitting second control information regarding one or more improveduser equipments supporting communication according to the distributedantenna system on a second resource region different from the firstresource region.

In accordance with another aspect of the present invention, there isprovided a base station for transmitting control information in adistributed antenna system, The base station comprises: a plurality ofdistributed antennas spaced apart from each other by a predetermineddistance or more and a processor configured to control the distributedantennas to transmit first control information regarding one or morelegacy user equipments supporting communication according to acentralized antenna system on a first resource region and to control thedistributed antennas to transmit second control information regardingone or more improved user equipments supporting communication accordingto the distributed antenna system on a second resource region differentfrom the first resource region.

In accordance with another aspect of the present invention, there isprovided a method of receiving control information at an improved userequipment supporting communication according to a distributed antennasystem including a plurality of distributed antennas spaced apart fromeach other by a predetermined distance or more. The method comprises:receiving second control information regarding one or more improved userequipments including the improved user equipment from at least one ofthe distributed antennas, wherein the second control information isreceived on a second resource region different from a first resourceregion, on which first control information regarding one or more legacyuser equipments supporting communication according to a centralizedantenna system is transmitted.

In accordance with yet another aspect of the present invention, there isprovided an improved user equipment supporting communication accordingto a distributed antenna system including a plurality of distributedantennas spaced apart from each other by a predetermined distance ormore.

The user equipment comprises: a receiver configured to receive signalstransmitted from the distributed antennas and a processor configure tocontrol the receiver to receive second control information regarding oneor more improved user equipments including the improved user equipmentfrom at least one of the distributed antennas, wherein the processordetects the second control information on a second resource regiondifferent from a first resource region, on which first controlinformation regarding one or more legacy user equipments supportingcommunication according to a centralized antenna system is transmitted.

In the respective aspects of the present invention, the first controlinformation may be transmitted on the first resource region through eachof the distributed antennas, and the second control information may betransmitted on the second resource region through some or all of thedistributed antennas.

In the respective aspects of the present invention, control informationregarding a first user equipment group including one or more improveduser equipments may be transmitted on the second resource region througha first antenna group including one or more distributed antennas, andcontrol information regarding a second user equipment group includingone or more improved user equipments, which is different from the firstuser equipment group, may be transmitted on the second resource regionthrough a second antenna group including one or more distributedantennas.

In the respective aspects of the present invention, at least one of sizeinformation and position information of the second resource region, andstream number information may be transmitted to a user equipment.

In the respective aspects of the present invention, the second controlinformation may be advanced MAP (A-MAP) information or PDCCHinformation. If the second control information is the A-MAP information,the second resource region may be located at a Contiguous Resource Unit(CRU) in a primary frequency partition in which the first resourceregion is located or at a Distributed Resource Unit (DRU) in a frequencypartition except the primary frequency partition. If the second controlinformation is the PDCCH information, the second resource region may belocated at a predetermined number of symbols following a symbol(s) of asubframe at which the first resource region is located or at one or morePRBs in a PDSCH region of the subframe.

In accordance with one aspect of the present invention, there isprovided a method of transmitting control information at a base stationof a cell including a plurality of distributed antennas spaced apartfrom each other by a predetermined distance or more. The methodcomprises: transmitting first control information regarding a first userequipment group including one or more user equipments on a predeterminedresource region through a first antenna group comprising one or moredistributed antennas and transmitting second control informationregarding a second user equipment group including one or more userequipments, which is different from the first user equipment group, onthe predetermined resource region through a second antenna groupcomprising one or more distributed antennas.

In accordance with another aspect of the present invention, there isprovided a base station for transmitting control information in adistributed antenna system. The base station comprising: a plurality ofdistributed antennas spaced apart from each other by a predetermineddistance or more and a processor configured to control a first antennagroup including one or more distributed antennas to transmit firstcontrol information regarding a first user equipment group including oneor more user equipments on a predetermined resource region and tocontrol a second antenna group including one or more distributedantennas to transmit second control information regarding a second userequipment group including one or more user equipments, which isdifferent from the first user equipment group, on the predeterminedresource region.

In accordance with another aspect of the present invention, there isprovided a method of receiving control information at a user equipmentin a cell including a plurality of distributed antennas spaced apartfrom each other by a predetermined distance or more. The methodcomprises: receiving, from at least one of a plurality of antenna groupseach of which includes one or more distributed antennas and transmitscontrol information regarding different user equipment groups on apredetermined resource region, control information of a user equipmentgroup to which the user equipment belongs; and detecting controlinformation of the user equipment from the received control information.

In accordance with yet another aspect of the present invention, there isprovided a user equipment in a cell including a plurality of distributedantennas spaced apart from each other by a predetermined distance ormore. The user equipment comprises: a receiver configured to receivesignals transmitted from the distributed antennas and a processorconfigure to control the receiver to receive, from at least one of aplurality of antenna groups each of which includes one or moredistributed antennas and transmits control information regardingdifferent user equipment groups on a predetermined resource region,control information of a user equipment group to which the userequipment belongs; and to receive control information of the userequipment from the received control information.

In the respective aspects of the present invention, antenna informationindicating the first antenna group may be transmitted to the first userequipment group, and antenna information indicating the second antennagroup may be transmitted to the second user equipment group.

In the respective aspects of the present invention, the first controlinformation may be masked using an identifier of the first antennagroup, and the second control information may be masked using anidentifier of the second antenna group.

In the respective aspects of the present invention, the first controlinformation may be scrambled using a scrambling sequence correspondingto the first antenna group, and the second control information may bescrambled using a scrambling sequence corresponding to the secondantenna group.

In the respective aspects of the present invention, each user equipmentbelonging to the first user equipment group and the second userequipment group may transmit information regarding a preferred antennagroup which will transmit control information of the corresponding userequipment.

In the respective aspects of the present invention, the preferredantenna group information may include a reference signal identifier foreach antenna group.

The aforementioned technical solutions are only a part of theembodiments of the present invention, and various modifications to whichtechnical features of the present invention are applicable will beunderstood by those of ordinary skill in the art to which the presentinvention pertains, based on the following detailed description of thepresent invention.

Advantageous Effects

According to the present invention, it is possible to efficientlytransmit control information in a system based on a communicationstandard supporting multi-node coordinated transmission, i.e. amulti-node system.

According to the present invention, control information for differentuser equipments is transmitted from different antennas or nodes throughthe same time and frequency resources, thereby improving efficiency inoperation of a control channel.

Also, according to the present invention, information indicating anantenna or a node used to transmit control information or data of a userequipment, which is one of a plurality of nodes of a multi-node system,is provided to the user equipment. Consequently, it is possible for theuser equipment to effectively receive or detect control information ordata thereof.

Also, according to the present invention, in a situation in which animproved user equipment manufactured according to a standard that iscapable of supporting multi-node coordinated transmission and a legacyuser equipment manufactured according to a communication standard whichdoes not support multi-node coordinated transmission coexist, it ispossible to efficiently transmitting control information regarding theimproved user equipment.

It will be appreciated by persons skilled in the art that the effectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and other advantages ofthe present invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing an example of a DAS structure to which thepresent invention is applied.

FIG. 2 is a view showing an example of a DAS configuration to which thepresent invention is applied.

FIG. 3 is a view showing another example of the DAS configuration towhich the present invention is applied.

FIG. 4 is a block diagram showing components of a user equipment and abase station which implement the present invention.

FIG. 5 is a view showing an Orthogonal Frequency Division MultipleAccess (OFDMA) type signal processing procedure.

FIG. 6 is a view showing an example of a control region to which anA-MAP can be transmitted in IEEE 802.16m.

FIG. 7 is a view showing an example of a control region to which a PDCCHcan be transmitted in 3GPP LTE/LTE-A.

FIGS. 8 and 9 are views illustrating transmission of control informationin a DAS according to the present invention.

FIG. 10 is a view showing an example of a reference signal used in IEEE802.16m.

FIG. 11 is a view showing an example of a reference signal used in 3GPPLTE/LTE-A.

FIG. 12 is a view showing embodiments for signaling antenna informationto a user equipment.

FIG. 13 is a view showing an example of pilot patterns for two datastream transmission in IEEE 802.16m.

FIG. 14 is a view showing an example of an A-MAP structure in a primaryfrequency partition in IEEE 802.16m.

FIG. 15 is a view showing an example of pilot patterns for four datastream transmission in IEEE 802.16m.

BEST MODE

Hereinafter, the preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is to beunderstood that the detailed description, which will be disclosed alongwith the accompanying drawings, is intended to describe the exemplaryembodiments of the present invention, and is not intended to describe aunique embodiment through which the present invention can be carriedout. The following detailed description includes detailed matters toprovide full understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention can becarried out without the detailed matters. For example, a case in which amobile communication system will be described as being a 3GPP LTE systemor an IEEE 802.16m system in the following detailed description. Exceptfor matters unique in 3GPP LTE or IEEE 802.16m, however, the presentinvention may be applied to other arbitrary mobile communicationsystems.

In some cases, in order to prevent the concept of the present inventionfrom being ambiguous, structures and apparatuses of the known art willbe omitted, or will be shown in the form of a block diagram based onmain functions of each structure and apparatus. Also, wherever possible,the same reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

A wireless communication system, to which the present invention isapplied, includes at least one base station (BS) 11. Each base stationprovides a communication service to a user equipment (UE) located at aspecific geographical region (generally referred to as a cell). The userequipment may be fixed or movable. The user equipment may includevarious devices that communicate with a base station to transmit andreceive user data and/or various kinds of control information. The userequipment may be referred to as a Terminal Equipment (TE), a MobileStation (MS), a Mobile Terminal (MT), a User Terminal (UT), a SubscriberStation (SS), a wireless device, a Personal Digital Assistant (PDA), awireless modem, or a handheld device. The base station is a fixedstation that performs communication with a user equipment and/or anotherbase station and exchanges various kinds of data and control informationwith the user equipment and another base station. The base station maybe referred to by other terms such as an evolved-NodeB (eNB), a BaseTransceiver System (BTS), an Access Point (AP), and a processing server(PS).

A cell region, to which the base station provides a service, may bedivided into a plurality of smaller regions in order to improve systemperformance. Each smaller region may be referred to as a sector or asegment. A Cell Identity (Celll_ID or IDCell) is given based on theentire system, whereas a sector or segment identity is given based on acell region, to which the base station provides a service. Generally,user equipments may be distributed in a wireless communication system ina state in which the user equipments are fixed or movable. Each userequipment may communicate with one or more base stations through anUplink (UL) and a Downlink (DL) at an arbitrary moment.

The present invention may be applied to various kinds of multi-nodesystems. For example, embodiments of the present invention may beapplied to a distributed antenna system (DAS), a macro node havinglow-power RRHs, a multi-base station coordinated system, a pico- orfemto-cell coordinated system, and a combination thereof. In amulti-node system, one or more base stations connected to a plurality ofnodes may be coordinated to simultaneously transmit a signal to a userequipment or simultaneously receive a signal from the user equipment.

The DAS uses a plurality of distributed antennas connected to a basestation or a base station controller, which manages a plurality ofantennas spaced apart from each other by a predetermined distance ormore in an arbitrary geographical region (also referred to as a cell),through a cable or a dedicated line in order to perform communication.In the DAS, each antenna or each antenna group may be a node of themulti-node system according to the present invention. Each antenna ofthe DAS may serve as a subset of antennas provided at the base stationor the base station controller. That is, the DAS is a kind of multi-nodesystem, and a distributed antenna or antenna group is a kind of node ina multi-antenna system. The DAS is different from a centralized antennasystem (CAS), in which a plurality of antennas is concentrated at thecenter of a cell, in that a plurality of antennas provided at the DAS isspaced apart from each other by a predetermined distance in a cell. TheDAS is different from a femto- or pico-cell coordinated system in thatall antennas located in a cell are not managed by a distributed antennaor a distributed antenna group but are managed by a base station or abase station controller at the center of the cell. Also, the DAS isdifferent from an ad-hoc network or a relay system which uses a basestation connected to a relay station (RS) in a wireless fashion in thatdistributed antennas are connected to each other via a cable or adedicated line. Also, the DAS is different from a repeater which simplyamplifies and transmits a signal in that a distributed antenna or adistributed antenna group transmits a signal different from anotherdistributed antenna or another distributed antenna group to a userequipment located adjacent to a corresponding antenna or a correspondingantenna group according to a command from a base station or a basestation controller.

The respective nodes of the multi-base station coordinated system or thefemto- or pico-cell coordinated system serve as independent basestations and cooperate with each other. Consequently, each base stationof the multi-base station coordinated system or the femto- or pico-cellcoordinated system may be a node of the multi-node system according tothe present invention. The multiple nodes of the multi-base stationcoordinated system or the femto- or pico-cell coordinated system areconnected to each other through a backbone network and performscheduling and/or handover together, thereby performing coordinatedtransmission or reception. A system in which a plurality of base stationparticipates in coordinated transmission as described above may bereferred to as a Coordinated Multi-Point (CoMP) system.

Various kinds of multi-node systems, such as the DAS, the macro nodehaving low-power RRHs, the multi-base station coordinated system, andthe pico- or femto-cell coordinated system, are different from eachother. However, since these systems are different from a single-nodesystem (for example, the CAS, the conventional MIMO system, theconventional relay system, the conventional repeater system, etc.), anda plurality of nodes of these systems are coordinated to participate inproviding a communication service to a user equipment, embodiments ofthe present invention may be applied to all of these systems.Hereinafter, the present invention will be described mainly based on theDAS as an example for the convenience of description. However, thefollowing description is merely an illustration. Also, an antenna or anantenna group of the DAS may correspond to a node of another multi-nodesystem, and a base station of the DAS may correspond to one or morecoordinated base stations of another multi-node system. Consequently,the present invention may also be applied to another multi-node systemin the same manner.

FIG. 1 is a view showing an example of a DAS structure to which thepresent invention is applied. A base station shown in FIG. 1 may includea plurality of antennas located at the center of a cell according to aCAS. For the convenience of description, however, only DAS antennas areshown in FIG. 1.

Referring to FIG. 1, a DAS, in which a plurality of antennas connectedto a single base station located in a cell in a wired fashion isdistributed at various positions in the cell, may be variouslyimplemented according to the number and position of the antennas. Forexample, a plurality of antennas may be distributed at predeterminedintervals in the cell, or two or more antennas may be located at aspecific position in a dense state. In the DAS, in a case in whichcoverage of the distributed antennas overlap irrespective of the form inwhich the distributed antennas are located in the cell, it is possibleto transmit a signal having rank 2 or more. For reference, rankindicates the number of transmission layers (3GPP LTE term) or thenumber of transmission streams (IEEE 802.16 term) that can besimultaneously transmitted through one or more antennas. For example,for spatial multiplexing in SU-MIMO, rank may be defined as the numberof transmission layers or the number of transmission streams that can beused by a user allocated to a predetermined resource region. Spatialmultiplexing serves to simultaneously transmit different signals usingone or more antennas. For reference, a transmission layer or atransmission stream is an output value of a layer mapper 303 and meansan information path input to a precoder. A transmission layer or a layeris a term used in 3GPP. In IEEE 802.16, an information path input to aprecoder 304 is referred to as a transmission stream, or an MIMO stream,or a data stream. In IEEE 802.16, on the other hand, an MIMO layer is aninformation path input to an MIMO encoder corresponding to the layermapper 303 in IEEE 802.16. In IEEE 802.16, an MIMO layer represents achannel coding block.

Referring to FIG. 1, a base station serving a cell region is connectedto a total of 8 antennas in a wired fashion. The respective antennas maybe located in the cell at regular intervals having a predetermineddistance or more or at various intervals. In the DAS, it is notnecessary to use all of the antennas connected to the base station. Aproper number of antennas may be used based on a signal transmissionrange of each antenna, a degree of coverage overlap of neighboringantennas, an interference effect between neighboring antennas, and thedistance between each antenna and a mobile user equipment.

For example, in a case in which three user equipments (UE1 to UE3) arelocated in the cell, and UE1 is located within signal transmissionranges of ANT1, ANT2, ANT7, and ANT8, as shown in FIG. 1, UE1 mayreceive a signal from one or more selected from among ANT1, ANT2, ANT7,and ANT8. On the other hand, the distance between UE1 and ANT3, ANT4,ANT5, and ANT6 is great with the result that path loss may occur, andpower consumption may increase. Also, signals transmitted from ANT3,ANT4, ANT5, and ANT6 may be negligible.

As another example, UE2 is located at a portion at which signaltransmission ranges of ANT 6 and ANT7 overlap with the result thatsignals transmitted through the other antennas are negligible except ANT6 and ANT7. UE3 is located within a distance close to ANT3, andtherefore, only a signal transmitted from ANT 3, of signals transmittedfrom ANT1 to ANT8, is dominant.

In a case in which a plurality of antennas is spaced apart from eachother in the cell, as shown in FIG. 1, the DAS may be operated as anMIMO system. The base station may communicate with UE1 through antennagroup 1 including at least one of ANT1, ANT2, ANT7, and ANT5. At thesame time, the base station may communicate with UE2 through antennagroup 2 including at least one of ANT6 and ANT7. At the same time, thebase station may communicate with UE3 through ANT5. At this time, ANT 4and ANT5 may perform transmission for UE3 and UE2, respectively, or maybe turned off.

That is, when the DAS communicates with a single user or a plurality ofusers, various numbers of data streams may be transmitted to each userequipment, and the antenna or the antenna group assigned to each mobileuser equipment located in the cell served by the base station may bevariously present. Based on the position of each mobile user equipmentlocated in the cell, the antenna or the antenna group performingcommunication with the corresponding user equipment may be specified butmay be adaptively changed depending upon movement of each mobile userequipment in the cell.

FIG. 2 is a view showing an example of a DAS configuration to which thepresent invention is applied.

Referring to FIG. 2, the DAS includes a base station and antenna nodesconnected to the base station. The antenna nodes are connected to thebase station in a wired/wireless fashion. Each of the antenna nodes mayinclude one to several antennas. Generally, antennas belonging to oneantenna node have characteristics that the distance between the nearestantennas is less than a few meters, and therefore, the antennas belongto the same regional spot. An antenna node serves as an access point, towhich a user equipment can access. The antenna node may also be referredto as an antenna cluster.

FIG. 3 is a view showing another example of the DAS configuration towhich the present invention is applied. Specifically, FIG. 3 shows anexample of a system structure in a case in which a DAS is applied tocentralized antenna system using conventional cell-based multi antennas.

Referring to FIG. 3, a plurality of centralized antennas (CAs), thedistance between the antennas is less than the radius of a cell, andtherefore, the antennas exhibit similar path loss effects, may belocated at a region adjacent to a base station according to anembodiment of the present invention. Also, a plurality of distributedantennas (DAs), in which the distance between the antennas is equal toor greater than a predetermined value and is greater than the distancebetween the CAs, and therefore, the antennas exhibit different path losseffects, may be located in the cell region.

Each DA includes one or more antennas connected to the base station in awired fashion. Each DA may have the same meaning as an antenna node forDAS or an antenna node. One or more DAs form a DA group, thereby forminga DA zone.

A DA group includes one or more DAs. The DA group may be variablyconfigured depending upon the position or reception state of a userequipment or may be fixedly configured with the maximum number ofantennas used in MIMO. A DA zone is defined as a range within whichantennas constituting a DA group can transmit or receive a signal. Thecell region shown in FIG. 3 includes n DA zones. A user equipmentbelonging to each DA zone may perform communication with one or more ofthe DAs constituting the DA zone. Upon transmitting signals to userequipments belonging to DA zones, the base station may simultaneouslyuse DAs and CAs, thereby improving a transmission rate.

FIG. 3 shows a CAS structure using the conventional multi antennas inwhich the CAS includes a DAS so that a base station and user equipmentsuses the DAS. The positions of CAs and DAs are shown as being dividedfrom each other for simplicity of description. However, the positions ofCAs and DAs are not limited thereto. The CAs and DAs may be variouslypositioned in different embodiments.

Meanwhile, a cell region, to which the base station provides a service,may be divided into a plurality of smaller regions in order to improvesystem performance. Each smaller region may be referred to as a sectoror a segment. A Cell Identity (Celll_ID or IDCell) is given based on theentire system, whereas a sector or segment identity is given based on acell region, to which the base station provides a service. Generally,user equipments may be distributed in a wireless communication system ina state in which the user equipments are fixed or movable. Each userequipment may communicate with one or more base stations through anUplink (UL) and a Downlink (DL) at an arbitrary moment.

FIG. 3 shows a CAS structure using the conventional multi antennas inwhich the CAS includes a DAS so that a base station and user equipmentsuses the DAS. The positions of CAs and DAs are shown as being dividedfrom each other for simplicity of description. However, the positions ofCAs and DAs are not limited to the example illustrated in FIG. 3. TheCAs and DAs may be variously positioned in different embodiments.

As shown in FIGS. 1 to 3, an antenna or an antenna node supporting eachuser equipment may be defined. Particularly upon transmitting downlinkdata, different data for each antenna or each antenna node may betransmitted for different user equipments through the same time andfrequency resources. This is a kind of MU-MIMO operation to transmitdifferent data streams for each antenna or each antenna node throughselection of the antennas or the antenna nodes.

In the present invention, each antenna or each antenna node may be anantenna port. The antenna port is a logical antenna implemented by aphysical transmit antenna or a combination of a plurality of physicaltransmit antenna elements. Also, in the present invention, each antennaor each antenna node may be a virtual antenna. A signal transmitted by abeam precoded using a beam forming method may be recognized as beingtransmitted by an antenna. Such an antenna transmitting the precodedbeam is referred to as a virtual antenna. Also, in the presentinvention, antennas or antenna nodes may be divided according to areference signal (pilot). One or more antennas or antenna groupstransmitting the same reference signal or the same pilot mean a set ofone or more antennas transmitting the same reference signal or the samepilot. That is, each antenna or antenna mode of the present inventionmay be interpreted as a physical antenna, a set of physical antennas, anantenna port, a virtual antenna, or an antenna identified by a referencesignal or pilot. In embodiments of the present invention, which willhereinafter be described, an antenna or an antenna node may be oneselected from among a physical antenna, a set of physical antennas, anantenna port, a virtual antenna, and an antenna identified by areference signal or pilot. Hereinafter, a physical antenna, a set ofphysical antennas, an antenna port, a virtual antenna, and an antennaidentified by a reference signal or pilot will generally be referred toas an antenna or an antenna node.

FIG. 4 is a block diagram showing components of a user equipment and abase station which implement the present invention.

A user equipment (UE) 12 serves as a transmitting device on an uplinkand as a receiving device on a downlink. On the other hand, a basestation (BS) 11 may serve as a receiving device on the uplink and as atransmitting device on the downlink.

The user equipment 12 and the base station 11 include antennas 500 a and500 b to receive information and/or data, signals, and messages,transmitters 100 a and 100 b to transmit messages by controlling theantennas 500 a and 500 b, receivers 300 a and 300 b to receive messagesby controlling the antennas 500 a and 500 b, and memories 200 a and 200b to store various kinds of information associated with communication ina wireless communication system, respectively. Also, the user equipment12 and the base station 11 further include processors 400 a and 400 b,respectively, which are configured to implement the present invention bycontrolling the components of the user equipment 12 and the base station11, such as the transmitters, the receivers, and the memories. Thetransmitters 100 a and 100 b, the memories 200 a and 200 b, thereceivers 300 a and 300 b, the processors 400 a and 400 b, and theantennas 500 a and 500 b in the user equipment 12 and the base stationmay cooperated with each other. The transmitter 100 a, the receiver 300a, the memory 200 a, and the processor 400 a in the user equipment 12may be configured as independent components on separate chips or theirseparate chips may be incorporated into a single chip. In the samemanner, the transmitter 100 b, the receiver 300 b, the memory 200 b, andthe processor 400 b in the base station 11 may be configured asindependent components on separate chips or their separate chips may beincorporated into a single chip. A transmitter and a receiver may beconfigured as a single transceiver in the user equipment or the basestation. The antennas 500 a and 500 b serve to transmit signalsgenerated from the transmitters 100 a and 100 b to the outside, or totransfer radio signals received from the outside to the receivers 300 aand 300 b. A transceiver module supporting a Multiple Input MultipleOutput (MIMO) function to transmit and receive data using a plurality ofantennas may be connected to two or more antennas.

The processors 400 a and 400 b generally control overall operations ofvarious modules of the user equipment 12 and the base station 11.Especially, the processors 400 a and 400 b may carry out various controlfunctions to implement the present invention, a Medium Access Control(MAC) frame variable control function based on service characteristicsand a propagation environment, a power saving mode function to controlidle-mode operations, a handover function, and an authentication andencryption function. The processors 400 a and 400 b may also be referredto as controllers, microcontrollers, microprocessors, microcomputers,etc. Meanwhile, the processors 400 a and 400 b may be configured ashardware, firmware, software, or a combination thereof. In a hardwareconfiguration, the processors 400 a and 400 b may be provided with oneor more Application Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), or Field Programmable Gate Arrays(FPGAs), which is configured to implement the present invention. On theother hand, in a firmware or software configuration, firmware orsoftware may be configured to include a module, a procedure, or afunction, which performs functions or operations of the presentinvention. The firmware or software configured to implement the presentinvention may be provided in the processors 400 a and 400 b, or may bestored in the memories 200 a and 200 b so that the firmware or softwarecan be driven by the processors 400 a and 400 b.

The transmitters 100 a and 100 b perform predetermined coding andmodulation with respect to signals and/or data, which are scheduled bythe processors 400 a and 400 b or schedulers connected to the processors400 a and 400 b and transmitted to the outside, and then transfer themodulated signals and/or data to the antennas 500 a and 500 b. Forexample, the transmitters 100 a and 100 b convert a transmission datastream into K signal trains by demultiplexing, channel coding,modulation, etc. The K signal trains are transmitted through theantennas 500 a and 500 b after being processed in transmissionprocessors of the transmitters. The transmitters 100 a and 100 b and thereceivers 300 a and 300 b of the user equipment 12 and the base station11 may be configured in different manners depending on procedures ofprocessing transmitted signals and received signals.

FIG. 5 is a view showing an Orthogonal Frequency Division MultipleAccess (OFDMA) type signal processing procedure.

A transmitter in a user equipment or a base station may transmit one ormore codewords. The one or more codewords may be scrambled by scramblers301 and may be modulated as complex symbols by modulation mappers 302. Alayer mapper 303 maps the complex symbols to one or more transmissionlayers, for example, M_(t) layers. For example, the layer mapper 303 maymap N complex symbols per layer.

According to IEEE 802.16, the layer mapper 303 may be implemented as anMIMO encoder (not shown). The MIMO encoder may encode one or more datatrains to be transmitted using a predetermined coding method to formcoded data, and may modulate the coded data to arrange the coded data assymbols to express positions on signal constellation. A data train is aninformation path input to the MIMO encoder. A data train indicates achannel coding block. According to IEEE 802.16, an information pathinput to the MIMO encoder is referred to as an MIMO layer. Meanwhile,the MIMO encoder may define layers of input symbols so that the precoder304 can distribute a specific symbol of an antenna to the path of thecorresponding antenna. That is, the MIMO encoder maps L MIMO layers intoM_(t) MIMO streams. The MIMO encoder is a batch processor tosimultaneously process M input symbols. The M input symbols may beexpressed as an M×1 vector as follows.

$\begin{matrix}{s = \begin{bmatrix}s_{1} \\s_{2} \\\ldots \\s_{M}\end{bmatrix}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Where, Si indicates an n-th input symbol of a batch. One or moresuccessive symbols may belong to an MIMO layer. A procedure of mappingthe input symbols from MIMO layers to MIMO streams is first performed ina spatial dimension. Output of the MIMO encoder, which serves as aninput of the precoder 304, may be expressed as an M_(t)×N_(F) MIMO STCmatrix as follows.

x=S(s)  Equation 2

Where, M_(t) indicates the number of MIMO streams, N_(F) indicates thenumber of subcarriers occupied by an MIMO block, x indicaes an output ofthe MIMO encoder, s indicates an input MIMO layer vector, s( ) indicatesa function to map the input MIMO layer vector to an STC matrix, and S(s)indicates an STC matrix.

The STC matrix x may be expressed as follows.

$\begin{matrix}{x = \begin{bmatrix}x_{1,1} & x_{1,2} & \ldots & x_{1,N_{F}} \\x_{2,1} & x_{2,2} & \ldots & x_{2,N_{F}} \\\ldots & \ldots & \ldots & \ldots \\x_{M_{t},1} & x_{M_{t},2} & \ldots & x_{M_{t},N_{F}}\end{bmatrix}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

The MIMO encoder may use various coding methods, such as SFBC, verticalencoding, multi-layer encoding, and CDR.

—SFBC Encoding

In SFBC encoding, an input to the MIMO encoder may be expressed as a 2×1vector.

$\begin{matrix}{s = \begin{bmatrix}s_{1} \\s_{2}\end{bmatrix}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

In a case in which encoding is performed using an SFBC encoding method,the MIMO encoder generates an SFBC matrix, which is a 2×2 matrix, asfollows.

$\begin{matrix}{x = \begin{bmatrix}s_{1} & {- s_{2}^{*}} \\s_{2} & s_{1}^{*}\end{bmatrix}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

The SFBC matrix occupies two successive subcarriers.

—Vertical Encoding

In SFBC encoding, an input and output of the MIMO encoder may beexpressed as an M×1 vector as follows.

$\begin{matrix}{x = {s = \begin{bmatrix}s_{1} \\s_{2} \\\ldots \\s_{M}\end{bmatrix}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

Where, s_(i) indicates an i-th input symbol in a batch. In the verticalencoding, s₁ . . . s_(m) belong to the same MIMO layer.

—Multi-Layer Encoding

In the case of multi-layer encoding, an input and output of the MIMOencoder may be expressed as an M×1 vector as follows.

$\begin{matrix}{x = {s = \begin{bmatrix}s_{1} \\s_{2} \\\ldots \\s_{M}\end{bmatrix}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

Where, s_(i) indicates an i-th input symbol in a batch. In themulti-layer encoding, s₁ . . . s_(m) belong to different MIMO layers.One or more successive symbols may belong to the same MIMO layer.

—Conjugate Data Repetition (CDR) Encoding

In the case of CDR encoding, an input to the MIMO encoder may beexpressed as a 1×1 vector as follows.

s=s ₁  Equation 8

In a case in which encoding is performed using an CDR encoding method,the MIMO encoder generates a CDR matrix, which occupies two successivesubcarriers, as follows.

x=[s ₁ s ₁*]  Equation 9

The precoder 304 multiplies complex symbols of a transmission layer by apredetermined precoding matrix selected according to channel status, forexample, a N_(t)×M_(t) precoder matrix W, and outputs the multiplicationresult as complex symbols for N_(t) antennas. The output of the precoder304 may be expressed as a N_(t)×N_(F) matrix as follows.

$\begin{matrix}{z = {{Wx} = \begin{bmatrix}z_{1,1} & z_{1,2} & \ldots & x_{1,N_{F}} \\z_{2,1} & x_{2,2} & \ldots & x_{2,N_{F}} \\\ldots & \ldots & \ldots & \ldots \\z_{N_{t},1} & x_{N_{t},2} & \ldots & x_{N_{t},N_{F}}\end{bmatrix}}} & {{Equation}\mspace{14mu} 10}\end{matrix}$

Where, N_(t) indicates the number of transmit antennas, and Z_(j,k)indicates an output symbol to be transmitted on a k-th subcarrierthrough a j-th antenna.

The precoder 304 may use both a codebook method and a non-codebookmethod. The complex symbols for each antenna are mapped totime-frequency resource elements used in transmission by resourceelement mappers 305. The complex symbols for each antenna mapped totime-frequency resource elements are modulated by the OFDMA signalgenerator 306 using an OFDMA method and are transmitted to therespective antenna or the respective antenna ports in the form of OFDMAsymbols (also referred to as OFDM symbols) for each antenna or eachantenna port. The OFDMA signal generator may perform Inverse FastFourier Transform (IFFT) with respect to the input symbols. A cyclicprefix (CP) may be inserted into time domain symbols upon which IFFT hasbeen performed. The OFDMA symbols are transmitted through the respectiveantennas.

In 3GPP LTE and IEEE 802.16, similar terms may designate differentobjects. Hereinafter, an information path input to the layer mapper 303will be referred to as an MIMO layer, and an information path outputfrom the layer mapper 303 will be referred to as a data stream, in orderto prevent confusion and for the convenience of description.

Although, in FIG. 5, the signal processing procedure using theOrthogonal Frequency Division Multiple Access (OFDMA) method isdescribed as an example, a user equipment may process an uplink signalusing a Single Carrier Frequency Division Multiple Access (SC-FDMA)method and may transmit the processed uplink signal to a base station.AN SC-FDMA type transmitter may include a scrambler 301, a modulationmapper 302, a precoder 304, and a resource element mapper 305. Thescrambler 301 of the user equipment scrambles a transmission signalusing a specific scrambling signal of the user equipment. The modulationmapper 302 modulates the scrambled signal into a complex symbol usingBPSK, QPSK, or 16 QAM according to the kind of the transmission signaland/or channel status. The modulated complex symbol is precoded by theprecoder 304, and is mapped to a time-frequency resource element to beused in real transmission by the resource element mapper 305. The signalmapped to the resource element may be transmitted to the base stationthrough the antenna in the form of an SC-FDMA signal. The user equipmentadopting the SC-FDMA signal processing method may include an SC-FDMAsignal generator to convert the signal mapped to the resource elementinto an SC-FDMA signal.

Although the OFDMA method is mainly used for downlink transmission sinceit is possible to increase frequency efficiency and cell capacity, theOFDMA method may also be used for uplink transmission. The userequipment may be configured to adopt both the OFDMA method and theSC-FDMA signal processing method. Also, the user equipment may bedesigned so that the both methods can be switched according to a channelenvironment.

Although, in FIG. 5, the scramblers 301, the modulation mappers 302, thelayer mapper 303, the precoder 304, the resource element members 305,the OFDM signal generators 306 are described as being included in thetransmitters 100 a and 100 b, the processors 400 a and 400 b may bedesigned to include the above operational modules. The transmitters 100a and 100 b may modulate OFDMA symbol signals into radio frequency (RF)signals and may transmit the modulated signals to the antennas 500 a and500 b. The antennas 500 a and 500 b of the receiving device may receivethe RF signals and may transmit the received RF signals to the receivers300 a and 300 b. The receivers 300 a and 300 b may modulate the RFsignals into OFDMA symbol signals and may provide the modulated signalsto the processors 400 a and 400 b.

Control Channel Allocation for Each Antenna or Antenna Node

In a communication standard, given time, space, and frequency resourcesare divided into various regions according to uses to prescribeinformation and characteristics of signals to be transmitted on theregions. Information which a base station transmits to a user equipmentthrough a downlink may be divided into information for all equipmentwithin coverage of the base station and information for a specific userequipment(s).

For example, system parameters, such as a cell ID or the number ofantennas of the base station, may be information for all use equipments.On the other hand, control information, such as uplink power controlinformation, response information for Hybrid Automatic Repeat reQuest(HARQ) ACKnowledge/Negative-ACKnowledge (ACK/NACK), or data informationrequested by a user equipment may be information for a specific userequipment.

Generally, information for all user equipments is present at apredetermined position of a specific channel so that all user equipmentscan access the information. For example, Physical Broadcast Channel(PBCH) and Physical Control Format Indicator Channel (PCFICH) of 3GPPLTE/LTE-A and Frame Control Header (FCH) or SuperFrame Header (SFH) ofIEEE 802.16 e/m are channels, through which information for all userequipments is transmitted. The information is transmitted usingdesignated time and frequency resources.

On the other hand, information for a specific user equipment or userequipment group is transmitted using different time and frequencyresources except when an MU-MIMO method is used. In order for a userequipment to access information for the user equipment, therefore, mapinformation indicating to which resource region the information has beenallocated is necessary. On a downlink, such map information istransmitted through a DL/UL MAP and/or an Advanced-MAP (A-MAP) in IEEE802.16e/m and through a Physical Downlink Control Channel (PDCCH) in3GPP LTE/LTE-A. Hereinafter, a wireless resource, through which such mapinformation is transmitted, will be referred to as a “control channel”,and a wireless resource region having a predetermined range, to whichone or more control channels can be allocated, will be referred to as a“control region”. For example, a PDCCH or an A-MAP may be referred to asa control channel, and a predetermined time and/or frequency resourceregion, to which a PDCCH or an A-MAP can be allocated, may be referredto as a control region. In particular, a resource region, on which aPDCCH or an A-MAP can be allocated or transmitted, will hereinafter bereferred to as a PDCCH/A-MAP region.

Information necessary to receive or detect data for a user equipment(s),such as Modulation and Coding Scheme (MCS) level information, istransmitted together with resource allocation information through thecontrol channel. Also, control information for each user equipment, suchas power control information, may also be transmitted.

FIG. 6 is a view showing an example of a control region on which anA-MAP can be transmitted in IEEE 802.16m, and FIG. 7 is a view showingan example of a control region on which a PDCCH can be transmitted in3GPP LTE/LTE-A.

Referring to FIG. 6, a radio frame structure used in IEEE 802.16 mayinclude a 20 ms superframe supporting a bandwidth of 5 MHz, 8.75 MHz, 10MHz, or 20 MHz. The superframe may include four 5 ms frames F0 to F3 ofthe same size, and begins with a SuperFrame Header (SFH). The SuperFrameHeader carries an essential system parameter and system configurationinformation. The SuperFrame Header may be located at a first subframe inthe superframe. A frame may include 8 subframes SF0 to SF7. Subframesare allocated to downlink or uplink transmission. Each subframe includesa plurality of OFDMA symbols in a time domain and a plurality ofresource units (RUs) in a frequency domain. Each RU includes a pluralityof subcarriers in the frequency domain. The OFDMA symbols may bereferred to as OFDMA symbols or SC-FDMA symbols according to multiaccess methods. The number of OFDMA symbols included in each subframemay be variously changed according to the bandwidth of a channel and thelength of a Cyclic Prefix (CP). The type of a subframe may be definedbased on the number of OFDMA symbols included in the subframe. Forexample, type-1 subframe may be defined as including 6 OFDMA symbols,type-2 subframe may be defined as including 7 OFDMA symbols, type-3subframe may be defined as including 5 OFDMA symbols, and type-4subframe may be defined as including 9 OFDMA symbols. A subframe mayinclude the same type of subframes or different types of subframes. FIG.6 illustrates type-1 subframe in which a subframe includes 6 OFDMAsymbols for the convenience of description. However, embodiments of thepresent invention, which will hereinafter be described, may also beapplied to different types of subframes in the same manner. Forreference, in IEEE 802.16, a resource including an OFDMA symbol and asubcarrier is also referred to as a tone.

An A-MAP of IEEE 802.16m is transmitted per downlink subframe. In a casein which flexible/fractional frequency reuse (FFR) is applied to adownlink subframe, a reuse-1 partition and/or a power-boosted reuse-3partition may include an A-MAP region. Although not shown, an uplinkcontrol channel carrying uplink control information in an uplinksubframe is also located at the reuse-1 partition or the power-boostedreuse-3 partition.

For reference, FFR is a technology that is capable of differentlysetting a frequency reuse factor to be applied to different frequencypartitions. In OFDMA, a system band is divided on a per subcarrierbasis. Consequently, a signal is transmitted on each subcarrier, and allsubcarriers are necessarily used in signal transmission. It is possibleto simultaneously increase throughput of users at the center of a celland users at the border of the cell (edge of the cell) using suchcharacteristics. Specifically, a central region of the cell is adjacentto the base station, and therefore, the central region of the cell issafe from co-channel interference from a neighboring cell. Consequently,the users at the center of the cell can use all possible subcarriers. Onthe other hand, the users at the border of the cell can only some of allpossible subcarriers. At the borders of the neighboring cells,frequencies are allocated to the cells so that the respective cells canuse different subcarriers. This is referred to as flexible/fractionalfrequency reuse (FFR). In IEEE 802.16m, the system band may be dividedinto a maximum of 4 frequency partitions. Power may be differentlyallocated to the respective frequency partitions to boost power of aspecific frequency partition. Each frequency partition is divided intoone or more resource units (RUs). The frequency partitions are indexedfrom a lower logical resource unit (LRU) index to a higher LRU index. Atthis time, a frequency partition including the lowest LRU index may be areuse-1 partition, which is followed by three reuse-3 partitions or tworeuse-2 partitions. A power-boosted reuse-3 partition is one of thereuse-3 partitions to which high power is allocated.

Referring to FIG. 7, a radio frame structure used in 3GPP LTE/LTE-A hasa length of 10 ms (327200 Ts) and includes 10 subframes of a uniformsize. Each of the subframes has a length of 1 ms and includes two slots.Each slot has a length of 0.5 ms. Here, Ts indicates sampling time, andTs is expressed as Ts=1/(2048×15 kHz). Each slot includes a plurality ofOFDMA symbols in a time domain and a plurality of resource blocks in afrequency domain. Each resource block includes a plurality ofsubcarriers in the frequency domain. The OFDMA symbols may be referredto as OFDMA symbols or SC-FDMA symbols according to multi accessmethods. The number of OFDMA symbols included in a slot may be variouslychanged according to the bandwidth of a channel and the length of a CP.For example, in the case of a normal CP, a slot includes 7 OFDMAsymbols. On the other hand, in the case of an extended CP, a slotincludes 6 OFDMA symbols. FIG. 7 illustrates a subframe in which a slotincludes 7 OFDMA symbols for the convenience of description. However,embodiments of the present invention, which will hereinafter bedescribed, may also be applied to different types of subframes in thesame manner. For reference, in 3GPP LTE/LTE-A, a resource including anOFDMA symbol and a subcarrier is also referred to as a resource element(RE).

In 3GPP LTE/LTE-A, each subframe includes a control region and a dataregion. The control region includes one or more OFDMA symbols startingfrom a first OFDMA symbol. The size of the control region may beindependently set for each subframe. For reference, a PCFICH and aPhysical Hybrid automatic retransmit request Indicator CHannel (PHICH)as well as a PDCCH may be allocated to the control region

As shown in FIGS. 6 and 7, control information is transmitted to a userequipment using predetermined time and frequency resources, which areparts of the wireless resources. Control information regarding a userequipment(s), including map information, is transmitted through thecontrol channel. Each user equipment detects and receives a controlchannel thereof from among control channels transmitted by the basestation. As the number of user equipments in a cell is increased,relative importance of resources occupied by such a control channel isincreased. With population of machine to machine (M2M) communication anda DAS in future, the number of user equipments in the cell will be muchmore increased. As a result, a control channel supporting such userequipments will be enlarged. That is, the number of OFDMA symbolsoccupied by a control channel in a subframe and/or the number ofsubcarriers occupied by a control channel in a subframe will beinevitably increased. Consequently, the present invention providesmethods of efficiently utilizing a control channel using thecharacteristics of a DAS.

According to the current communication standard based on a CAS, allantennas belonging to a base station transmit control channels (forexample, a MAP, an A-MAP, a PDCCH, etc.) regarding all user equipmentsin the base station on a control region. In order to obtain informationregarding an antenna node allocated to each user equipment and controlinformation, such as downlink/uplink resource allocation information,each user equipment must process the control region, which is a commonregion defined for control information transmission, to obtain controlinformation thereof. For example, each user equipment may obtain controlinformation thereof, which is one of the signals transmitted through thecontrol region, using a blind decoding method.

If each antenna transmits control information regarding all userequipments on the same control region according to the currentcommunication standard, all of the antennas transmit the same signal onthe control region, and therefore, implementation is easily achieved.However, if the size of control information to be transmitted isincreased due to the increase in number of user equipments covered bythe base station, an MU-MIMO operation, and additional controlinformation (for example, information regarding antenna nodes allocatedto the user equipments) for a DAS, the size or number of controlchannels is increased with the result that it may be difficult totransmit all control information through the conventional controlregion.

In order to efficiently use the control channel, the present inventionproposes a method of differently setting a user equipment(s), which isan object of control information transmission, for each antenna orantenna node. In this case, the user equipment may receive controlinformation from an antenna node or from a plurality of antenna nodes.According to the present invention, control information to betransmitted on a specific control region may be different for eachantenna or antenna node in the DAS. That is, in the present invention,user equipment groups are divided per antenna or antenna node, and eachantenna or antenna node transmits control information regarding acorresponding user equipment group. Control information regarding aplurality of user equipments may be multiplexed to a control channel andmay then be transmitted. Alternatively, a control channel may beconfigured with respect to each user equipment, and a plurality ofcontrol channels may be multiplexed to a control region and may then betransmitted.

In terms of a user equipment, user equipment groups to which controlinformation is to be transmitted for each base station antenna group maybe different from each other, and therefore, control informationreceived by the respective user equipments on the control region maydifferent from each other. Also, antenna groups which receive controlinformation from the respective user equipments may be different fromeach other. This is because user equipments multiplexed to apredetermined control channel or a predetermined control region aredifferent from each other.

Each user equipment may belong to one or more user equipment groups. Auser equipment group may be included in another user equipment group.User equipment groups including different user equipments may beregarded as different user equipment groups even if the user equipmentgroups share some user equipments. In a case in which the number of userequipments belonging to the respective user equipment groups and therespective user equipments are the same, however, the user equipmentsare regarded as belonging to a user equipment group. In a case in whicha user equipment belongs to a plurality of user equipment groups, theuser equipment may receive different control information or controlchannel sets on the control region from a corresponding antenna grouptransmitting signals to the plurality of user equipment groups.

The processor 400 b of the base station according to the presentinvention may group user equipments within coverage of the base stationinto user equipment groups, to which control information is transmitted.The processor 400 b may distribute the user equipments for each antennaor antenna node. Also, control information of user equipments allocatedto the same antenna or antenna node of the base station, i.e. controlinformation of user equipments belonging to the same user equipmentgroup, may be multiplexed to a predetermined control channel or controlregion. Under control of the processor 400 b, the precoder 100 b of thebase station may map control information of a user equipment(s)belonging to the same user equipment group to the same antenna orantenna node. Since a user equipment may belong to one or more userequipment groups, a user equipment belonging to a plurality of userequipment groups may be mapped to a plurality of antenna nodes.

A control information transmission method of the present inventionincludes an embodiment in which an antenna node set through which a basestation transmits control information to a user equipment and an antennanode set through which the base station transmits data to the userequipment are differently configured. Consequently, the base stationprocessor 400 b can control the precoder 100 b to map data to an antennanode different from an antenna node through which control information istransmitted. Also, the control information transmission method of thepresent invention includes an embodiment in which an antenna node setthrough which a base station receives control information from a userequipment and an antenna node set through which the base stationreceives data from the user equipment are differently configured.

FIGS. 8 and 9 are views illustrating transmission of control informationin a DAS according to the present invention.

Referring to FIG. 8, a DAS system of FIG. 8 includes antenna node 1consisting of ANT1 and ANT2 and antenna node 2 consisting of ANT3 andANT4. On the assumption that UE2 is within coverage of antenna node 1and coverage of antenna node 2, UE1 is within coverage of antenna node1, and UE3 is within coverage of antenna node 2, a base station of FIG.8 may transmit control information according to (a), (b), or (c) of FIG.9.

Referring to FIG. 9( a), all antennas of the base station transmitcontrol information for UE1, UE2, and UE3 in the same time and frequencyregions. That is, each antenna of the base station transmits controlinformation of UE1, UE2, and UE3 at a predetermined time using apredetermined frequency.

In embodiments of the present invention, user equipments supported in acontrol region for each antenna node are differently set to improveefficiency of a control channel. Referring to FIGS. 9( b) and 9(c),according to the present invention, antenna node 1 transmits controlinformation of UE1 and UE2 on predetermined time and frequencyresources, and antenna node 2 transmits control information of UE2 andUE3 on the predetermined time and frequency resources. Controlinformation for UE2 affected by all antenna nodes of FIG. 8 istransmitted from antenna node 1 and antenna node 2 using predeterminedresources. Control information for UE1 affected by antenna node 1consisting of ANT1 and ANT2 is transmitted from antenna node 1 using thesame resources as the predetermined resources. Control information forUE3 affected by antenna node 2 consisting of ANT3 and ANT4 istransmitted from antenna node 3 using the same resources as thepredetermined resources.

According to the present invention, as shown in FIG. 9( b), it ispossible to reduce resources to be allocated to the control channel orto support more user equipments using predetermined resources allocatedto the control channel. Otherwise, as shown in FIG. 9( c), it ispossible to transmit control information while increasing the amount ofthe control information using predetermined resources allocated to thecontrol channel. According to the present invention, therefore, it ispossible to improve efficiency of control information transmissionthrough the control region by differently setting a user equipment(s)allocated to the control region for each antenna node.

A plurality of antenna nodes may transmit control information using thesame resource to a user equipment moving at high speed, a legacy userequipment to which the present invention cannot be applied, or a userequipment the location of which is not clear as well as to a userequipment, such as UE2, within coverage of several antenna nodes.Consequently, the base station processor 400 b according to the presentinvention may control the transmitter 100 b to map control informationregarding a legacy user equipment, a user equipment moving at highspeed, or a user equipment the location of which is not clear to aplurality of antenna nodes.

For reference, FIG. 9 illustrates a case in which all antennas belongingto a specific antenna node transmit control information on the sameresource as an example. In a case in which all antennas belonging to aspecific antenna node transmit the same control information on the sameresource, it is possible to improve reliability of control informationtransmission. Alternatively, some of the antennas belong to the specificantenna node may transmit control information on the same resource, andthe remaining antennas may transmit other data, thereby obtaining spacemultiplexing gain.

In allocating an antenna or antenna node for control informationtransmission as described above, a user equipment may feed a preferredantenna or antenna node back to a base station in order to transmitcontrol information thereof. The base station may select an antenna orantenna node, through which control information is to be transmitted tothe user equipment, with reference to the information fed back by theuser equipment.

The user equipment may selectively uses a reference signal from theantenna or antenna node allocated thereto for transmission of controlinformation to selectively receive a data stream containing controlinformation thereof. Alternatively, the user equipment may receive aplurality of data streams and may detect a data stream containingcontrol information thereof from among the received data streams.

FIG. 10 is a view showing an example of a reference signal used in IEEE802.16m, and FIG. 11 is a view showing an example of a reference signalused in 3GPP LTE/LTE-A.

Referring to FIGS. 8 and 9, for example, it is assumed that ANT1transmits a reference signal RS for antenna 1, ANT2 transmits a RS forantenna 2, ANT3 transmits a RS for antenna 3, and ANT4 transmits a RSfor antenna 4. Although FIGS. 10 and 11 show reference signals withrespect to four transmit antenna to refer to the illustration used inFIGS. 8 and 9, the present invention may be applied to a DAS systemincluding a different number of antennas in the same manner.

Referring to FIG. 10, a different reference signal for each antenna maybe transmitted in IEEE 802.16m. Such a reference signal differentlydefined for each antenna is referred to as a midamble or a MIMO midamblein IEEE 802.16m. The midamble is a signal that can be used by all usersin a cell. The midamble may be used to select a Precoding MatrixIndicator/Index (PMI) in the case of closed loop MIMO and to calculate aChannel Quality Indicator/Index (CQI) in the case of open loop MIMO. Themidamble is transmitted in a second downlink subframe of each frame.Except a particular case, the midamble occupies a plurality of OFDMAsymbols in type-1 or type-2 subframe. Hereinafter, OFDMA symbolsoccupied by a midamble signal will be referred to as midamble symbols.The processor 400 a or the receiver 300 a of the user equipmentaccording to the present invention may include a module to calculate aPMI and/or a module to calculate a CQI using a midamble signal.

FIG. 10 shows an example of the structure of a midamble with respect toa 4Tx antenna. In FIG. 10, a subband is a resource allocation unitincluding a plurality of, such as four successive, resource units (RUs)in a frequency domain. Each resource unit includes a plurality ofsubcarriers. A subcarrier to which a midamble signal is allocated isalso referred to as a midamble subcarrier. In midamble symbols, a datasignal or no signal may be allocated to the other subcarrier, to whichno midamble signal is allocated. A subcarrier, to which a data signal isallocated, is also referred to as a data subcarrier, and a subcarrier,to which no signal is allocated and thus which transmits no signal, isalso referred to as a null subcarrier.

Each antenna transmits a midamble signal thereof through a correspondingsubcarrier. Each antenna does not transmit a signal through subcarriers,through which midamble signals of the other antennas are to betransmitted. For the convenience of description, a midamble signaltransmitted by ANTn is referred to as a ‘RSn’. Referring to FIGS. 8 and9, for example, ANT1 transmits RS1, ANT2 transmits RS2, ANT3 transmitsRS3, and ANT4 transmits RS4 on a corresponding one of a plurality ofsubcarriers constituting a first OFDMA symbol in a second subframe ofeach frame.

UE2 may estimate a PMI from RS1 to RS4 transmitted by ANT1 to ANT4 ormay calculate a CQI to receive control information allocated to UE2. UE1may estimate a PMI from RS1 and RS2 transmitted by ANT1 and ANT2 or maycalculate a CQI to receive or detect control information of UE1. Thatis, each user equipment may receive or detect corresponding controlinformation using only midamble signals from antennas or antenna nodestransmitting control information. To this end, the processor 400 a ofthe user equipment may estimate a PMI or calculate a CQI using only amidamble signal from an antenna or antenna node transmitting controlinformation of the user equipment. Under control of the processor 400 a,the receiver 300 a of the user equipment may receive or detect controlinformation of the user equipment.

Alternatively, UE1 may also estimate a PMI or calculate a CQI using allof RS1 to RS4. In this case, UE1 may configure a reception filter tominimize channel interference from ANT3 and ANT4 to receive controlinformation of UE1. That is, each user equipment may use midamblesignals from all antennas or antenna nodes, and, in this case, the userequipment may recognize channels from antennas or antenna nodestransmitting control information thereof and may configure a receptionfilter to minimize channel interference from antennas or antenna nodesnot transmitting control information thereof to efficiently receivecontrol information thereof. The processor 400 a of the user equipmentmay estimate a PMI or calculate a CQI using all midamble signalsreceived by the user equipment. Under control of the processor 400 a,the receiver 300 a of the user equipment may configure a receptionfilter to minimize channel interference from the antenna or antenna nodenot transmitting control information of the user equipment to receivecontrol information of the user equipment.

Referring to FIG. 11, an RS pattern is defined for each antenna in 3GPPLTE/LTE-A. In 3GPP LTE/LTE-A, such a reference signal differentlytransmitted for each antenna on a downlink is also referred to as acell-specific RS (CRS). The CRS enables the user equipment to estimate achannel with respect to a corresponding antenna. The processor 400 a orthe receiver 300 a of the user equipment may include a channelestimation module to estimate a channel with respect to a correspondingantenna based on the CRS. In the case of a system that is capable ofusing N_(t) antennas, the user equipment may estimate independent N_(t)channels.

FIG. 11 shows an example of a CRS pattern with respect to a 4Tx antenna.The CRS pattern means a pattern of resource elements which a referencesignal with respect to a specific antenna occupies in a resource blockpair.

Each antenna transmits a CRS thereof on resource elements occupied bythe CRS pattern. Each antenna does not transmit a signal on resourceelements on which CRSs of the other antennas are to be transmitted. Forthe convenience of description, a CRS transmitted by ANTn is referred toas a ‘RSn’. Referring to FIGS. 8 and 9, for example, ANT1 transmits RS1,ANT2 transmits RS2, ANT3 transmits RS3, and ANT4 transmits RS4 on acorresponding one of a plurality of subcarriers forming a first OFDMAsymbol in a second subframe of each frame.

UE2 may measure channel quality from ANT1 to ANT4 based on RS1 to RS4transmitted by ANT1 to ANT4 to receive control information allocated toUE2. UE1 may measure channel quality based on RS1 and RS2 transmitted byANT1 and ANT2 to receive control information allocated to UE1. That is,each user equipment may receive corresponding control information usingonly CRSs from antennas or antenna nodes transmitting controlinformation. The processor 400 a of the user equipment may control thereceiver 300 a using only a CRS from an antenna or antenna nodetransmitting control information of the user equipment. Under control ofthe processor 400 a, the receiver 300 a of the user equipment mayreceive control information of the user equipment or control informationregarding a user equipment group to which the user equipment belongs.

Alternatively, UE1 may also measure channel quality using all of RS1 toRS4. In this case, UE1 may configure a reception filter to minimizechannel interference from ANT3 and ANT4 to receive control informationof UE1. That is, each user equipment may use CRSs from all antennas orantenna nodes, and, in this case, the user equipment may recognizechannels from antennas or antenna nodes transmitting control informationthereof and may configure a reception filter to minimize channelinterference from antennas or antenna nodes not transmitting controlinformation thereof to efficiently receive control information. Theprocessor 400 a of the user equipment may estimate channel status usingthe CRSs from antennas or antenna nodes transmitting control informationof the user equipment, which is some of the CRSs received by thereceiver 300 a. Also, the processor 400 a of the user equipment maycontrol the receiver 300 a to configure a reception filter to minimizechannel interference from the antenna or antenna node not transmittingcontrol information of the user equipment using all of the CRSs receivedby the receiver 300 a. The receiver 300 a may receive controlinformation of the user equipment, which is part of various kinds ofcontrol information transmitted by the corresponding base station, usingthe reception filter.

Also, when a user equipment reads control information of the userequipment or a user equipment group to which the user equipment belongsto, may estimate a PMI from a corresponding reference signal, which isone of reference signals transmitted by antennas in a correspondingcell, or calculate/estimate channel quality to decode the correspondingcontrol information. For example, if a PDCCH or an A-MAP is transmittedonly through ANT1, the user equipment may estimate a PMI and/or estimatechannel quality based on RS1 transmitted by ANT1 to decode the PDCCH orthe A-MAP. Alternatively, the user equipment may estimate channelshaving interference signals from reference signals transmitted by theother antennas so that the estimated channels can be used when decodingthe corresponding control information. The processor 400 a of the userequipment may decode control information of the user equipment using thereference signal transmitted by the antenna used to transmit the controlinformation of the user equipment, which is one of the reference signalsreceived by the receiver 300 a.

The user equipment processor 400 a may decode data of the user equipmenttransmitted on the data region based on the control information of theuser equipment.

In a case in which different antennas or antenna nodes transmit controlinformation for different user equipments through the same time andfrequency resources as described above, it is possible to improvecontrol channel efficiency.

Antenna/Antenna Node Information

—Blind Decoding

The base station may mask control information to be transmitted to eachuser equipment using an identifier given to each user equipment and maytransmit the masked control information (S110). The base stationprocessor 400 b may generate control information of each user equipmentand may mask the control information of each user equipment using anidentifier of the corresponding user equipment. A STation IDentifier(STID) and a Radio Network Temporary Identifier (RNTI) may be used formasking. For example, the base station processor 400 b may mask (forexample, XOR operate) a sequence corresponding to an identifier of thecorresponding user equipment with respect to a Cyclic Redundancy Check(CRC) for error detection and may add the masked CRC to the generatedcontrol information. The base station processor 400 b channel-codes thecontrol information masked with the identifier of the user equipment(S120) to generate coded data and multiplexes control information ofuser equipments to be transmitted together at a predetermined antenna orantenna node (S130). The multiplexed control information is transmittedon a predetermined resource region through the predetermined antenna orantenna node via the transmitter 100 b of the base station, thescrambler 301, the modulation mapper 302, the layer mapper 303, theprecoder 304, the resource element mapper, and the OFDMA signalgenerator 306 (S140 to S190).

The user equipment may configure a plurality of reception filters withrespect to a combination of antennas or antenna nodes that can transmitthereto and may find control information thereof through demasking ofsignals having passed through the reception filters using the respectiveidentifiers thereof. The user equipment may recognize informationcorresponding to an antenna combination having the highest receptionperformance as control information thereof. The processor 400 a of theuser equipment may select a candidate group of antennas or antenna nodesthat can be allocated to the user equipment. The processor 400 a of theuser equipment may control the receiver 300 a to configure a receptionfilter for each combination of antennas or antenna nodes. The processor400 a may recognize information corresponding to an antenna combinationin which the intensity of a signal having passes through the receptionfilter is a predetermined level or more as an antenna combinationtransmitting control information regarding a user equipment group towhich the user equipment belongs. The processor 400 a demasks controlinformation having passed through the reception filter using theidentifier of the user equipment to detect a CRC error. The processor400 a may recognize control information having no error as controlinformation of the user equipment.

For example, referring to FIGS. 8 and 9, the user equipment mayconfigure reception filters with respect to antenna group 1 includingonly antenna node 1, antenna group 2 including only antenna node 2, andantenna group 3 including antenna node 1 and antenna node 2, and mayrecognize an antenna group corresponding to a reception filter havingthe highest reception performance as an antenna group having transmittedcontrol information of the user equipment. According to the presentinvention, as previously described with reference to FIG. 3, an antennagroup, which is a set of antennas and/or antenna nodes, may be referredto as a DA group. Control information or data of a user equipment(s)belonging to a user equipment group is transmitted by the user equipmentgroup. Referring to FIG. 9( a), antenna node 1 and antenna node 2belonging to antenna group 3 transmit control information of a userequipment group consisting of UE1 to UE3 on a control region. Referringto FIGS. 9( b) and 9(c), antenna group 1 including antenna node 1transmits control information of a user equipment group consisting ofUE1 and UE2 on a control region, and antenna group 2 including antennanode 2 transmits control information of a user equipment groupconsisting of UE2 and UE3 on the control region.

Even if a base station does not provide a user equipment withinformation of an antenna, antenna node, or antenna node grouptransmitting control information of the user equipment, the userequipment may find a space resource from which control informationcorresponding thereto is transmitted. Here, the space resource means anantenna or antenna node resource. The user equipment configures areception filter through all possible combinations of antennas in asituation in which the position and/or number of antennas carryingcontrol information is unknown and demasks a signal having passedthrough the reception filter using an identifier of the user equipmentto acquire information of the user equipment. If a signal for thecorresponding user equipment is not present in the detected resourceregion, demasking using the identifier of the user equipment may not bepossible.

—Signaling of Antenna/Antenna Node Information

In a case in which the user equipment has a single reception antenna,and therefore, it is difficult to sort signals introduced through thesame time and frequency resources through spatial signal processing orin a case in which intensities of signals received by the respectiveantenna nodes are greatly different from each other, and therefore, itis not difficult for the user equipment to receive control informationeven if transmit antenna or antenna node information is not known, itmay be unnecessary for the user equipment to recognize the antenna orantenna node information.

On the other hand, in a case in which the user equipment has multipleantennas, and therefore, the user equipment selectively receives a datastream corresponding thereto, which is one of a plurality of data steamsor in a case in which it is necessary for the user equipment to detect adata stream corresponding thereto from among a plurality of detecteddata streams, it may be advantageous for the user equipment to recognizeinformation from which antenna or antenna node is informationcorresponding thereto in improving reception performance of controlinformation.

As previously described with respect to the blind decoding, the userequipment may configure various reception filters based on antennagroups that can be allocated to the user equipment and may recognizeantennas or antenna nodes belonging to an antenna group corresponding toa reception filter having the highest reception performance as antennasor antenna nodes having transmitted control information of the userequipment.

However, if information regarding an antenna node transmitting controlinformation of the user equipment is transmitted to the user equipment,it may be possible for the user equipment to stably acquire controlinformation of the user equipment based on more correct informationregarding the antenna node. Hereinafter, therefore, embodiments forsignaling information (hereinafter, referred to as antenna information)indicating which antenna or antenna node transmits control informationto the user equipment, i.e. embodiments for signaling antennainformation to the user equipment, will be described with reference toFIG. 12. FIG. 12 is a view showing embodiments for signaling antennainformation to a user equipment.

Embodiment 1 Clear Signaling

A base station may transmit information regarding an antenna or antennanode allocated to transmit control information, i.e. antennainformation, to a corresponding user equipment(s).

In IEEE 802.16, the antenna information may be clearly signaled to auser equipment, for example, through an SFH, A-MAP IE, preamble, orMedium Access Control (MAC) message. In 3GPP LTE/LTE-A, the antennainformation may be clearly signaled to a user equipment, for example,through a PBSH, SIB, or MAC message.

The base station processor 400 b may generate at least one selected fromamong SFH IE containing antenna information regarding a user equipmentgroup, A-MAP IE, preamble sequence, PBCH, SIB, SCH, and MAC messages.Under control of the base station processor 400 b, the base stationtransmitter 100 b may transmit the antenna information to acorresponding user equipment.

The antenna information may include an index of an antenna nodetransmitting control information regarding corresponding user equipmentor a pattern index of a downlink reference signal to be received by thecorresponding user equipment. The downlink reference signal includes aCRS, a DeModulation Reference Signal (DMRS), a Channel StatusInformation Reference Signal (CSI-RS), pilot, and midamble. When thebase station transmits antenna information for transmission of controlinformation, the user equipment finds and receives control informationthereof in the control region using a reference signal corresponding toan antenna node(s) allocated thereto. The user equipment may acquiredata thereof, which are parts of data in the data region, based on thecontrol information.

Although, according to embodiment 1, the base station directly transmitsinformation indicating an antenna, antenna node, or antenna group fortransmission of control information to the user equipment, signaling maybe implicitly performed in an indirect fashion according to embodiment 2or embodiment 3 in order to reduce signaling overhead.

Embodiment 2 Masking for Each Antenna Group

A base station may transmit control information to each user equipmentin a state in which the control information is masked using anidentifier or index assigned to each antenna group (S110). The processor400 b of the base station may mask the control information of the userequipment using an identifier or index of an antenna group, to which thecontrol information of the user equipment will be transmitted. Forexample, the processor 400 b may mask (for example, XOR operate) asequence corresponding to an index of a corresponding antenna group withrespect to a 16-bit Cyclic Redundancy Check (CRC) so that the masked CRCcan be added to the control information of the user equipment.

The base station processor 400 b channel-codes the control informationmasked with the identifier or index of the antenna group (S120) togenerate coded data and multiplexes control information of userequipments to be transmitted together at a predetermined antenna orantenna node (S130). The multiplexed control information is transmittedon a predetermined resource region through the predetermined antenna orantenna node via the transmitter 100 b of the base station, thescrambler 301, the modulation mapper 302, the layer mapper 303, theprecoder 304, the resource element mapper, and the OFDMA signalgenerator 306 (S140 to S190).

Referring to FIGS. 8 and 9, it is assumed that an identifier or index isgiven to antenna group 1 including antenna node 1, antenna group 2including only antenna node 2, and antenna group 3 including antennanode 1 and antenna node 2. In a case in which ANT to ANT3 transmit thesame control information on the same resource as shown in FIG. 9( a),the base station may mask control information regarding UE1, UE2 and UE3using an identifier or index corresponding to antenna group 3 includingantenna node 1 and antenna node 2 and may transmit the masked controlinformation. Referring to FIGS. 9( b) and 9(c), the base station maymask control information regarding UE1 and UE2 using an identifier orindex corresponding to antenna group 1 including antenna node 1, maymask control information regarding UE2 and UE3 using an identifier orindex corresponding to antenna group 2 including antenna node 2, and maytransmit the masked control information to corresponding userequipments.

The user equipment may configure combinations of antennas that cantransmit to the user equipment and may find a control channeltransmitted to the user equipment through demasking of received controlchannels using an identifier or index of the corresponding antennacombination or group. The user equipment may recognize that controlinformation of the user equipment is included in the informationtransmitted through the control channel corresponding to the antennanode group having successfully performed demasking. The processor 400 aof the user equipment may configure a candidate group of antenna groupsthat can be allocated to the user equipment. The processor 400 a of theuser equipment may demask control information transmitted from thecontrol region using an identifier or index of each antenna group todetermine whether a CRC error is detected. The processor 400 a mayrecognize that the antenna group having the identifier or index with noCRC error has transmitted control information of the user equipment andthat the antenna group has transmitted control information regarding auser equipment group to which the user equipment belongs.

For example, referring to FIGS. 8 and 9, UE1 may configure antenna group1, antenna group 2, and antenna group 3 as a combination of antennasthat can be allocate thereto, may perform demasking using an identifieror index corresponding to each antenna group, and may recognizeeffectively demasked control information as control information of auser equipment group to which UE1 belongs.

According to embodiment 2 of the present invention, the user equipmentmay find a space resource, through which control informationcorresponding thereto is transmitted. Specifically, according toembodiment 2 of the present invention, the user equipment may configurea reception filter through all possible antenna groups in a situation inwhich the position and/or number of antenna nodes carrying controlinformation is unknown and may demask a signal having passed through thereception filter using an identifier or index of the antenna group tofind an antenna group having transmitted control information of the userequipment. In addition, the user equipment may detect controlinformation to which control information of the user equipment ismultiplexed.

Embodiment 3 Scrambling for Each Antenna Node

A base station may divide some or all of information regarding aplurality of user equipments multiplexed to the same resource for eachantenna, antenna node, or antenna group, may scramble the user equipmentinformation with a sequence having low correlation, and may transmit thescrambled user equipment information (S130). In this case, thescrambling sequence is a sequence corresponding to an antenna node orantenna group transmitting the information.

The base station processor 400 b masks control information of each userequipment using an identifier of the corresponding user equipment(S110),channel-codes the masked control information to generate coded data(S120), and multiplexes control information of user equipments to betransmitted together through a predetermined antenna or antenna node,i.e. the same antenna group (S130).

The base station processor 400 b may control the scrambler 301 toscramble control information to be transmitted through the same antennagroup with a scrambling sequence corresponding to the antenna group. Thescrambled control information is transmitted on a predetermined resourceregion through the antenna group via the modulation mapper 302, thelayer mapper 303, the precoder 304, the resource element mapper, and theOFDMA signal generator 306 (S450 to S190).

The user equipment may descramble the received signals with a scramblingsequence of each antenna group to recognize information having highsignal intensity as a control channel through which control informationof the user equipment has been transmitted. The processor 400 a of theuser equipment may configure a candidate group of antenna groups thatcan be allocated to the user equipment. Under control of the processor400 a of the user equipment, the receiver 300 a of the user equipmentmay perform descrambling with an identifier or index of an antenna groupbelonging to the candidate group. As a result of descrambling, theprocessor 400 a of the user equipment may recognize that controlinformation of the user equipment is included in control informationhaving more than a predetermined level of signal intensity. In addition,the processor 400 a may recognize the antenna group corresponding to thescrambling sequence having more than the predetermined level of signalintensity as a node having transmitted the control information of theuser equipment. That is, the user equipment may indirectly acquireantenna information using a scrambling sequence assigned to each antennagroup.

In embodiment 3, the user equipment receives a control channel usingsequences corresponding to various combinations of all antennas orantenna nodes given in the system in a state in which an antenna,antenna node, or antenna group allocated to the user equipment is notrecognized. The user equipment may recognize N_(upper) antenna nodes orantenna groups having relatively high receiving performance as antennanodes allocated thereto or may decide an arbitrary number of antennanodes as an antenna node candidate group for the user equipment. Aninteger N_(upper) may be prescribed as a standard, may be transmittedthrough a PSCH, SFH, or FCH as a system parameter, or may be transmittedthrough a PDCCH, a Physical Downlink Shared CHannel (PDSCH), MAP, orA-MAP as control information.

The above-described embodiments 1 to 3 may be applied to an inventionrelated to allocation of control information to an antenna or antennanode previously described with reference to FIGS. 6 to 9. A combinationof embodiments 1 to 3 may be applied to the invention. For example, ifcontrol information regarding each user equipment group is masked usingan identifier of an antenna group allocated to the user equipment groupas in embodiment 2, embodiment 3 may further be applied so that the userequipment can more correctly recognize antennas or antenna information.

For reference, the antenna group is a concept including all antennanodes or all antennas. Consequently, an antenna group may be replaced byan antenna node or an antenna.

Meanwhile, the user equipment may separate control information of theuser equipment from control information regarding a user equipment groupto which the user equipment belongs. The user equipment may demaskcontrol information belonging to the user equipment group using anidentifier of the user equipment and, if no CRC error is detected, maydetect control information of the user equipment. That is, the processor400 a of the user equipment may demask control information of userequipments belonging to the user equipment group using an identifier ofthe user equipment and may determine control information from which noCRC error is detected as control information of the user equipment.

Since the base station masks control information of a user equipmentusing an identifier of the user equipment, the user equipment may decidea candidate group of antenna nodes allocated to the user equipment usingan identifier or index of an antenna node or antenna group and maydecide the final antenna node using the identifier of the userequipment. Also, the user equipment may receive control information of auser equipment group to which the user equipment belongs using anidentifier or index of an antenna node or antenna group and may detectcontrol information of the user equipment from control information ofthe user equipment group using the identifier of the user equipment.

Alternatively, the user equipment may narrow a candidate group ofantenna nodes allocated to the user equipment using an identifier of theuser equipment and may make the final decision using an identifier orindex of an antenna node or antenna group. Otherwise, the user equipmentmay recognize an antenna node set having the best reception performanceas an antenna node set allocated to the user equipment simultaneouslyusing an identifier of the user equipment and an identifier or index ofan antenna node. Control information of the user equipment is maskedusing an identifier of the user equipment and, in addition, the controlinformation is masked using an identifier or index of an antenna node orantenna group to process the control information once again so that theuser equipment can more clearly find a corresponding antenna or antennanode.

The user equipment may use received power information of a referencesignal for each reference signal pattern allocated for each antenna orantenna node in order to obtain antenna information.

The user equipment recognizes an antenna node or antenna group allocatedthereto using one or more selected from among information received foreach antenna node using an index or identifier of an antenna node,information received for each user equipment using an identifier of auser equipment, and reception intensity information of a referencesignal, and receives control information transmitted through thecorresponding antenna node or antenna group.

Meanwhile, in blind decoding, if a signal for a user equipment ispresent but a combination of antennas configured by the user equipmentis different from a real combination of antennas provided by a basestation, the user equipment may obtain a very noisy signal even if theuser equipment performs demasking using an identifier of the userequipment. Also, in embodiment 2, if a combination of antennasconfigured by the user equipment is different from a real combination ofantennas provided by a base station, it is not possible to demask areceived signal. Also, even in embodiment 3, if a combination ofantennas configured by the user equipment is different from a realcombination of antennas provided by a base station, a scramblingsequence is changed, and therefore, it is not possible for the userequipment to correctly obtain control information from signalstransmitted from the base station.

In order to solve this problem, the base station may signal informationregarding a combination of antennas that can be allocated to the userequipment (hereinafter, referred to as antenna combination information)to the user equipment. For example, the base station processor 400 b maygenerate antenna combination information regarding a combination ofantennas or antenna nodes that can be allocated to an arbitrary userequipment entering a corresponding cell and may control the transmitter100 b to broadcast the antenna combination information. Upon enteringthe corresponding cell, the user equipment acquires the antennacombination information to prevent a combination of antennas arbitrarilyselected by the user equipment from being different from a combinationof antennas that can be actually supported by the base station.Information regarding a combination of antennas that can be provided bythe base station may be transmitted to the user equipment through abroadcast signal.

Referring to FIGS. 8 and 9, the base station of FIG. 8 may signalinformation regarding antenna group 1 including antenna node 1, antennagroup 2 including antenna node 2, and antenna group 3 including antennanode 1 and antenna node 2 to user equipments within coverage of the basestation as antenna combination information. In performing blinddecoding, demasking according to embodiment 2, and descramblingaccording to embodiment 3, UE1 to UE3 may perform the blind decoding,the demasking, and the descrambling using identifiers or indices ofantenna group 1 to antenna group 3 based on the antenna combinationinformation signaled by the base station instead of arbitrarilyconfiguring a candidate group of antenna groups.

When the user equipment is turned on or enters a new cell, the userequipment performs an initial cell detecting operation, such assynchronization with the base station. To this end, the user equipmentmay receive a synchronization signal from the base station tosynchronize with the base station and to acquire information, such as acell identifier, etc. In IEEE 802.16m, a Primary Advanced preamble(PA-preamble) and a Secondary Advanced preamble (SA-preamble) are used.In 3GPP LTE/LTE-A, a Primary Synchronization Channel (P-SCH) and aSecondary Synchronization Channel (S-SCH) are used as thesynchronization signal. In IEEE 802.16m, the PA-preamble is used toobtain a system bandwidth and carrier configuration information, and theSA-preamble is used to obtain a cell identifier. In 3GPP LTE/LTE-A, theP-SCH is used to obtain time or frequency domain synchronization, suchas OFDMA symbol synchronization and slot synchronization, and the S-SCHis used to obtain a cell identifier and/or CP configuration informationof a cell. For reference, a synchronization signal transmission positionin a radio frame is generally fixed. The user equipment synchronizedwith the base may receive a PBCH, FCH, or SFH from the base station toacquire broadcast information in the cell.

In 3GPP LTE/LTE-A, the PBCH contains a master information block (MIB)including the most frequently transmitted parameters which are necessaryfor a user equipment to initially access a network of a correspondingbase station. The master information block includes parameters, such asa downlink system bandwidth, PHICH configuration, and a system framenumber (SFN). The base station according to the present invention maysignal antenna combination information to the user equipment, forexample, through a PBCH transmitted every frame. The user equipment mayreceive the PBCH to clearly recognize the antenna combinationinformation as well as the downlink system bandwidth, the PHICHconfiguration, and the SFN.

In IEEE 802.16e/m, the FCH or the SFH carries an essential systemparameter and system configuration information. The user equipment mayreceive an SFH transmitted every superframe to recognize the essentialsystem parameter and system configuration information. For example, theSFH carries a superframe number, a primary frequency partition positionto which an A-MAP region can be allotted, and frequency partitionposition information for an uplink control channel. The base stationaccording to the present invention may signal antenna combinationinformation to the user equipment, for example, through the SFH.

Meanwhile, in a case in which control information is transmitted foreach antenna node, as proposed in the present invention, a userequipment or a user equipment group to which control information istransmitted, a user equipment or a user equipment group to which data istransmitted, and a user equipment or a user equipment group from whichuplink information is transmitted may different from each other in termsof the antenna node. For example, referring to FIGS. 8 and 9, UE2receives control information from both antenna node 1 and antenna node 2but may receive data from only antenna node 1 or antenna node 2. Thatis, even in a case in which the DAS base station according to thepresent invention performs transmission (SU-MIMO transmission) in whichmultiple antennas perform a transmission for a single user equipment onthe same resource when transmitting control information to a specificuser equipment, the DAS base station may support different userequipments (MU-MIMO transmission) using the same resource even whentransmitting data.

In a case in which an antenna node transmitting control information andan antenna node transmitting data are different from each other, antennainformation signaled from the base station to the user equipment maycorrespond to the antenna node transmitting data or the antenna nodetransmitting control information. As a result, an antenna node indicatedby the antenna information may be different from an antenna nodeactually transmitting control information or an antenna node actuallytransmitting data.

In order to overcome disagreement between the antenna node indicated bythe antenna information and the antenna node actually transmitting dataor control information, the base station according to the presentinvention may separately inform the respective user equipments ofinformation regarding antenna nodes transmitting control information ofthe respective user equipment and information regarding antenna nodestransmitting data. Information indicating an antenna transmitting dataor control information may be transmitted to the user equipment, forexample, in the form of an antenna node index or an antenna group index.Also, for example, in a case in which information regarding an antennanode transmitting control information is signaled to the user equipmentby default, information regarding an antenna node transmitting data maybe signaled to the user equipment in the form of a difference between anindex of the antenna node or antenna group transmitting the controlinformation and an index of the antenna node or antenna grouptransmitting the data. On the other hand, in a case in which informationregarding an antenna node transmitting data is signaled to the userequipment by default, information regarding an antenna node transmittingcontrol information may be signaled to the user equipment in the form ofa difference between an index of the antenna node or antenna grouptransmitting the data and an index of the antenna node or antenna grouptransmitting the control information.

Information regarding an antenna node transmitting data may be signaledto the user equipment through the control information. For example, thebase station processor 400 b may generate control information includinginformation regarding an antenna node which will support a correspondinguser equipment in a data region and may control the base stationtransmitter 100 b to allocate or transmit the control information to awireless resource according to the control information allocation schemeof the present invention as previously described.

If the standard prescribes agreement between an antenna nodetransmitting control information and an antenna node transmitting data,the base station may signal only information regarding an antenna nodetransmitting control information or information regarding an antennanode transmitting data to the user equipment.

Meanwhile, the user equipment may transmit information regarding anantenna, antenna node, or antenna group preferred by the user equipmentto the base station of the corresponding cell. The information mayinclude an identifier of a reference signal distinguished for eachantenna, antenna node, or antenna group. The processor 400 a of the userequipment may estimates an antenna or antenna node having good channelstatus using a downlink signal and may control the transmitter 100 a ofthe user equipment based thereon to transmit to the user equipmentinformation regarding an antenna node which the base station wishes touse when transmitting downlink control information or data to the userequipment. In a case in which agreement between an antenna nodetransmitting control information and an antenna node transmitting datais not necessary, the user equipment may separately provide antennainformation preferred to transmit control information and antennainformation preferred to transmit data to the base station. Theprocessor 400 b of the base station may allocate an antenna node whichwill transmit control information or data regarding the user equipmentwith reference to the antenna node preferred for control information ordata provided by the user equipment.

Although, in the above description, embodiments for transmitting antennainformation transmitting control information to the user equipment weredescribed, the above-described embodiments may be applied to a case inwhich antenna information transmitting data is transmitted to the userequipment in the same manner. That is, information regarding an antennanode transmitting data may be clearly transmitted to the correspondinguser equipment, data may be transmitted after being masked using anidentifier of the corresponding user equipment or an identifier or indexof an antenna group, or some or all data may be transmitted after beingscrambled for each antenna group.

Relationship with Legacy User Equipments

In the above description, a method of transmitting control informationfor different user equipments from different antennas or antenna nodesthrough the same time and frequency resources was described. Also,embodiments for transmitting antenna information together with thecontrol information were described. In a case in which theabove-described proposals of the present invention are applied to IEEE802.16 and 3GPP LTE, how to support legacy user equipments operatingbased on the conventional IEEE 802.16e/m or 3GPP LTE/LTE-A standard maycome into question.

For operation of legacy user equipments, control information regardingthe legacy user equipments may be transmitted using all antennas withina predetermined control region, and control information regarding userequipments (hereinafter, referred to as DAS user equipments) operatingbased on the above proposals may be separately transmitted for eachantenna node or antenna group in the predetermined control region.

However, a method of transmitting control information regarding thelegacy user equipments and the DAS user equipments on the same controlregion may badly affect performance improvement of the DAS userequipments due to restrictions required in transmission of a controlchannel in the current IEEE 802.16m and 3GPP LTE/LTE-A standards.

FIG. 13 is a view showing an example of pilot patterns for two datastream transmission in IEEE 802.16m. FIG. 13( a) shows a basic pilotpattern on stream 0, which is the first one of the two data streams, andFIG. 13( b) shows a basic pilot pattern on stream 1, which is the secondone of the two data streams.

For example, according to the IEEE 802.16m standard, various A-MAPinformation elements (IEs) in an A-MAP region are converted into twoMIMO layers through channel coding. The two MIMO layers are convertedinto two data streams by SFBC encoding performed by the MIMO encoder303. The two data streams, SFBC encoded and output from the MIMO encoder303, are precoded by the precoder 304 using a N_(t)×2 precoding matrixbased on the number N_(t) of transmit antennas and are transmittedthrough the respective transmit antennas.

Even if the number of the transmit antennas of the base station isgreater than 2, the base station transmits a pilot using only two pilotpatterns through an antenna grouping method in the A-MAP region. Even ifan A-MAP is received from a base station having more than 2 transmitantennas, therefore, the user equipment can recognize only two datastreams. In a case in which such a method is applied to the DAS in orderto stably transmit an A-MAP, several antennas, which are spread out, aredivided into two antenna groups. The first antenna group simultaneouslytransmit the A-MAP using a first pilot pattern, and the second antennagroup simultaneously transmit the A-MAP using a second pilot pattern. Atthis time, it is advantageous for each antenna group to secure coveragewithin which each antenna group reaches all regions in a cell. However,this pilot transmission method is not proper to maximize systemefficiency in the DAS. Specially, an SFBC method used for A-MAPtransmission is a kind of transmit diversity method, in which twosymbols are alternately transmitted to two data streams. Consequently,each stream is not proper to be transmitted to different user equipmentsin an environment in which the difference between two stream receptionintensities of user equipments is great as in the DAS. For example, in acase in which two distributed antennas are present, for a terminal thatcan receive a signal from only one of the two antennas, only noise ispresent in one of two physical channels receiving symbols, and suchnoise may be estimated as a channel. When the symbol is received usingthis, therefore, reception performance may be greatly lowered due toamplified noise channel.

In a case in which it is necessary to differently set user equipmentstransmitting control information for each antenna node in the DAS as inthe above-described proposal of the present invention, greaterdifference between pilot reception intensities is preferable for theuser equipments. In other words, in a case in which the differencebetween the intensity of a signal from an antenna node adjacent to auser equipment and the intensity of a signal from an antenna nodedistant from the user equipment is great, interference between theantenna nodes is low, and therefore, it is possible to simultaneouslytransmit different control information for each antenna node todifferent user equipments. Low signal interference between the antennanodes is an essential factor to transmit information important in datareception and/or decoding, such as an A-MAP, to the user equipment.However, if an A-MAP must be unconditionally transmitted using two pilotpatterns as required in IEEE 802.16m, all of the DAS antennas must betransmitted after being virtualized so that all of the DAS antennas canbe recognized as two antennas in the control region. This may restrictcontrol channel efficiency improvement of DAS user equipments (userequipments configured according to a standard supporting the DAS afterIEEE 802.16m) receiving control information on the control region. Forexample, in a case which DAS antennas are densely arranged, thereception intensity of two pilots transmitted from two antenna groups tothe user equipment become great. In a case in which control informationof two user equipment is transmitted on the same resource according tothe scheme proposed by the present invention, signal interferencebetween the two pilots is great with the result that a controlinformation transmission rate of the two user equipment may be reduced.Also, a great number of antennas or antenna nodes may be present in theDAS. If an A-MAP is transmitted through only two data streams accordingto the conventional method, the A-MAP may be simultaneously transmittedto a maximum of two user equipments.

In 3GPP LTE/LTE-A, on the other hand, a PDCCH may be transmitted using aCRS only through a single antenna or in a transmit diversity mode. Thecurrent 3GPP LTE/LTE-A does not prescribe that a plurality of antennasor antenna nodes belonging to a specific base station transmitsdifferent PDCCHs through the same resource. For example, if a PDCCH istransmitted through a single antenna, a codeword is mapped to a datastream. That is, the number M_(t) of data steams output from the layermapper 303 is 1, and, even if a base station includes a plurality oftransmit antennas, the base station transmits the PDCCH through aphysical antenna or a virtual antenna based on an antenna groupingmethod. Even if the user equipment receives the PDCCH from a basestation including a plurality of transmit antennas, therefore, the userequipment can recognize only one data stream. As another example, if aPDCCH is transmitted in a diversity mode, a codeword is mapped to two orfour data streams. At this time, it is prescribed that only one codewordcan be transmitted on the same resource. In the PDCCH, therefore, multiuser MIMO transmission, which transmits multiple codewords using thesame resource, is not possible.

For multi user MIMO transmission, the PDCCH must be transmitted in aspace multiplexing mode. Although not prescribed in the currentLTE/LTE-A, the user equipment must receive the PDCCH using a CRS even ifthe PDCCH can be transmitted in a space multiplexing mode. Multi userMIMO transmission using the CRS is not impossible, but the base stationmust notify even a PMI applied to a data stream transmitted to each userequipment and a PMI applied to a data stream transmitted to another userequipment to the respective user equipments. For this reason, the multiuser MIMO transmission has great overhead and is complicated.

Also, in a case in which control information is transmitted on the sameresource to a plurality of user equipments using the CRS, a referencesignal for each combination of antennas has to be defined. Consequently,implementation is complicated, and overhead in transmission of thereference signal is increased.

In conclusion, only an A-MAP with respect to a maximum of two userequipments can be transmitted on the same resource according to thecurrent IEEE 802.16 standard, and only a PDCCH can be transmitted on thesame resource according to the current 3GPP LTE/LTE-A standard.

In order to solve the above problems, the present invention defines anew control channel for DAS user equipments and provides a method oftransmitting the new control channel on a resource different from theconventional control channel. The DAS user equipments are implemented torecognize corresponding control information from the new controlchannel. Hereinafter, a control channel defined according to thestandard prescribed under the current CAS system will be referred to asa CAS-control channel, and the above channel for the DAS will bereferred to as a DAS-control channel. Also, a predetermined time and/orfrequency resource to which the CAS-control channel can be allocatedwill be referred to as a CAS-control region, and a predetermined timeand/or frequency resource to which the SAS-control channel can beallocated will be referred to as a SAS-control region. In addition, userequipments which do not support a function according to the DAS standardwill be referred to as legacy user equipments or CAS user equipments,and user equipments implemented according to the DAS standard will bereferred to as DAS user equipments.

According to a standard prescribed in the current IEEE 802.16m or 3GPPLTE/LTE-A, control information regarding CAS user equipments, which arelegacy user equipments, may be transmitted to the CAS user equipmentsusing all antennas of the base station within the conventional controlregion. In a case in which a new standard prescribes that controlinformation regarding DAS user equipments moving at high speed must betransmitted through all antennas, control information regarding the DASuser equipments as well as the CAS user equipment may be transmitted tothe corresponding user equipments though the conventional controlregion. Control information regarding DAS user equipments moving at lowspeed may be transmitted to the corresponding user equipments through anew control channel.

The base station processor 400 b may control the base stationtransmitter 100 b to allocate control information of the legacy userequipments to the CAS-control channel and to allocate controlinformation of the DAS user equipments to the DAS-control channel newlydefined for the DAS user equipments. Under control of the base stationprocessor 400 b, the base station transmitter 100 b may transmit theCAS-control channel on the CAS-control region and may transmit theDAS-control channel on a resource region different from the CAS-controlregion.

Allocation information indicating the size and/or position of theDAS-control region may be transmitted through an upper message or may betransmitted on the CAS-control region. The base station processor 400 bmay generate an upper message including the allocation informationindicating the size and/or position of the DAS-control region and maycontrol the base station transmitter 100 b to transmit the uppermessage. Alternatively, the base station processor 400 b may generatethe allocation information and may control the base station transmitter100 b to transmit the allocation information on the CAS-control region.

Also, the number of MIMO streams or the number of reference signals orpilots used in the DAS-control region may be different from the numberof MIMO streams or the number of reference signals or pilots used in theCAS-control region. Consequently, information indicating the number ofMIMO streams or the number of reference signals or pilots may betransmitted through an upper message or may be transmitted on theCAS-control region. The base station processor 400 b may generate anupper message including information indicating the number of MIMOstreams or the number of reference signals or pilots used in theDAS-control region and may control the base station transmitter 100 b totransmit the upper message. Alternatively, the base station processor400 b may generate the information and may control the base stationtransmitter 100 b to transmit the information on the CAS-control region.

In transmitting control information through the DAS-control channel,information regarding an antenna node allocated to a user equipment maybe signaled to the user equipment according to at least one of theabove-described embodiments 1 to 3. That is, the above-describedembodiments 1 to 3 for signaling antenna information may be combinedwith the present method of transmitting control information to a userequipment through the DAS-control region to maintain compatibility withlegacy user equipments.

Hereinafter, embodiments in which the DAS is applied to IEEE 802.16 andembodiments in which the DAS is applied to 3GPP LTE will be described.

—DAS According to IEEE 802.16

A MAP region for DAS different from the conventional A-MAP region(hereinafter, referred to as a CAS A-MAP region) is further provided forDAS user equipments. The MAP region for DAS (hereinafter, referred to asa DAS-MAP region) is a region on which a DAS-MAP carrying controlinformation regarding user equipments based on a new standard supportingthe DAS. A-MAP IEs (for example, an assignment A-MAP IE, HARQ feedbackA-MAP IE, power control A-MAP IE, non-user specific A-MAP IE, etc.) arepartially or entirely transmitted to the DAS-MAP. Also, an additional IEfor DAS operation may be transmitted using the DAS-MAP region except thecurrent A-MAP IE which is not related to the DAS. In the new DAS-MAPregion, a pilot pattern divided for each antenna, antenna node, orspecific antenna group is used to transmit control information accordingto the present invention.

For reference, a non-user specific A-MAP includes information which isnot limited to a specific user or a specific user group. The userequipment decodes the non-user specific A-MAP in the primary frequencypartition to acquire information necessary to decode an assignment A-MAPand a HARQ feedback A-MAP. For example, the non-user specific A-MAP maycarry parameters, such as transmission parameters used to calculate thesize of the assignment A-MAP and an index of the HARQ feedback A-MAP.The HARQ feedback A-MAP carries HARQ ACK/NACK information for uplinkdata transmission, and a power control A-MAP carries a fast powercontrol command to the user equipment. The assignment A-MAP includesresource allocation information divided into several types of assignmentA-MAP IEs. Each assignment A-MAP IE is separately coded to carryinformation regarding a user equipment or user equipment group.

FIG. 14 is a view showing an example of an A-MAP structure in a primaryfrequency partition in IEEE 802.16m.

According to current IEEE 802.16, an A-MAP region is present at aDistributed Logical Resource Unit (DLRU) position in a primary frequencypartition, such as a reuse-1 partition or a power-boosted reuse-3partition. For example, in the case of a subframe of a superframe excepta first subframe, an A-MAP region includes initial L_(AMAP) DLRUs. Onthe other hand, in the case of the first subframe of the superframe, anA-MAP region includes L_(AMAP) DLRUs following the initial L_(AMAP)DLRUs occupied by an SFH. LRUs are formed from Physical Resource Units(PRUs). Each PRU is a basic physical unit of resource assignmentincluding P_(sc) successive subcarriers and N_(sym) successive OFDMAsymbols. For example, each PRU may include P_(sc)=18 subcarriers, andmay include N_(sym)=6, 7, and 5 OFDMA symbols with respect to type-1,type-2, and type-3 subframes, respectively. Each LRU is a basic unit fordistributed or localized resource assignment. A resource occupied byeach A-MAP may be changed depending upon system configuration andscheduler operation.

The DAS-MAP region proposed by the present invention may include DLRUsdifferent from the CAS-MAP region.

Embodiments regarding configuration of the DAS-MAP region will bedescribed as follows.

(1) Embodiment X

In the DAS-MAP region, an A-MAP IE for each DAS user equipment istransmitted, and information which is not specific to a specific DASuser equipment is transmitted through the conventional non-user specificA-MAP IE. That is, DAS user equipments may share some or all of non-userspecific A-MAP IEs with legacy user equipments. The non-user specificA-MAP IEs carry various kinds of information necessary for the userequipments to recognize user specific A-MAP IEs. In a case in which userspecific A-MAP IEs to be transmitted on the DAS-MAP region and userspecific A-MAP IEs to be transmitted on the CAS A-MAP region areconfigured by common parameters, therefore, it may not be necessary toseparately configure non-user specific IEs in the DAS-MAP region.

A legacy user equipment may decode a non-user specific A-MAP IEtransmitted on the CAS A-MAP region in the primary frequency partitionand may acquire information necessary to decode a user specific A-MAP IEin the CAS A-MAP region using the non-user specific A-MAP IE. The DASuser equipment may decode a non-user specific A-MAP IE transmitted onthe CAS A-MAP region in the primary frequency partition and may acquireinformation necessary to decode a user specific A-MAP IE in the DAS-MAPregion using the non-user specific A-MAP IE.

(2) Embodiment Y

In the same manner as in embodiment X, legacy user equipments and DASuser equipments share some or all of non-user specific A-MAP IEs. Unlikeembodiment X in which the DAS user equipments do not share user specificA-MAP IEs with the legacy user equipments, however, the DAS userequipments according to embodiment Y may share some or all of the userspecific A-MAPs.

For example, user specific A-MAP IEs transmitted for legacy userequipments are information that can be transmitted even for DAS userequipments without change. Consequently, some or all selected from amonga HARQ feedback A-MAP IE, allocation A-MAP IE, power control A-MAP IEmay be transmitted on the CAS A-MAP region, and information added forDAS operation may be transmitted on the DAS-MAP region. The informationadded for DAS operation may include transmit antenna information used indata transmission from the data region.

As another example, A-MAP IEs regarding the legacy user equipments maybe transmitted on the CAS A-MAP region, and A-MAP IEs regarding the DASuser equipments may be transmitted through the A-MAP region or theDAS-MAP region.

Each DAS user equipment may blind decode the CAS A-MAP region and theDAS-MAP region to find an A-MAP IE thereof. At this time, in order toreduce computing power of the user equipment necessary for blinddecoding, when an event in which the transmission structure of a radioframe will be changed due to cell entry, reentry, node change, etc. hasoccurred, the base station may semi-statically transmit an A-MAP IE ofthe user equipment so that the user equipment performs blind decodingonly in a first subframe received after the event has occurred. The userequipment may perform blind decoding only with respect to the firstsubframe to detect an A-MAP IE thereof, and may receive or detect anA-MAP IE on a region from which the A-MAP IE has been transmittedwithout blind decoding with respect to subframes following the firstsubframe. However, the region from which the A-MAP IE is transmitted maybe changed depending upon various situations, such as the position ofthe user equipment or traffic of the base station. Indicationinformation regarding whether the region on which the A-MAP IE istransmitted is changed at the next subframe may be signaled to the userequipment through a MAC message or a user specific A-MAP IE (forexample, an allocation A-MAP IE).

Alternatively, indication information regarding whether the region onwhich the A-MAP IE is transmitted is a CAS A-MAP region or a DAS-MAPregion may be added to a predetermined region of the CAS A-MAP region orthe DAS-MAP region. The user equipment may first read the indicationinformation in the predetermined region to recognize a region on whichan A-MAP IE thereof is transmitted. The user equipment may perform blinddecoding at the region indicated by the indication information to obtainan A-MAP IE thereof.

(3) Embodiment W

An A-MAP IE regarding a DAS user equipment is transmitted through aDAS-MAP region. A non-user specific A-MAP IE and a user specific A-MAPIE regarding a legacy user equipment are transmitted on a CAS A-MAPregion, and a non-user specific A-MAP IE and a user specific A-MAP IEregarding a DAS user equipment are transmitted on the DAS-MAP region.Unlike embodiment X and embodiment Y, an A-MAP IE for an DAS userequipment is not transmitted on an A-MAP region. Consequently, the DASuser equipment acquires a non-user specific A-MAP IE for a DAS userequipment and an A-MAP IE regarding DAS user equipment on the DAS-MAPregion.

In the above-described embodiments X to W, the position and/or size ofthe DAS-MAP region may be previously set according to a standard. Forexample, the DAS-MAP region may be defined to be configured by initialL_(DASMAP) DLRUs in a predetermined frequency partition except theprimary frequency partition in which the CAS A-MAP region is located.

In the above-described embodiments X to W, the position and/or size ofthe DAS-MAP region may not be previously set according to a standard butmay be signaled to the user equipment through an SFH (P-SFH IE or S-SFHIE) or MAC message (for example, an Advanced Air Interface SystemConfiguration Descriptor (AAI_SCD) message or an AAI DownLinkInterference Mitigation parameter (AAI_DL_IM) message).

The base station processor 400 b according to the present invention maygenerate A-MAP IEs necessary for DAS user equipments and may allocatethe A-MAP IEs to the CAS A-MAP region or the DAS-MAP region according toany one of embodiments X to W. Under control of the base stationprocessor 400 b, the base station transmitter 100 b may transmit IEs tobe accessed by legacy user equipments after being allocated to the CASA-MAP region and may transmit IEs to be accessed by DAS user equipmentsafter being allocated to the CAS A-MAP region or the DAS-MAP regionaccording to any one of embodiments X to W.

The processor 400 a of each DAS user equipment may acquire an A-MAP IEnecessary therefor according to any one of embodiments X to W. Undercontrol of the processor 400 b, the receiver 300 a of each DAS userequipment may receive an A-MAP necessary for reception and/or decodingof data thereof on the CAS A-MAP region or the DAS-MAP region. Theprocessor 400 a may control the receiver 300 a to receive and/or decodedata thereof transmitted on the data region using A-MAP IEs carried bythe A-MAP.

According to the present invention, the DAS-MAP region is located at aContiguous RU (CRU) or a Distributed resource unit (DRU) at which theCAS A-MAP region is not present. LRUs may be divided into DistributedLRUs (DLRUs) which are distributed throughout the whole frequency bandsof a physical channel and Contiguous LRUs (CLRUs) which are concentratedat a specific frequency band of the physical channel. Each CLRU may bedivided into a subband CLRU and a miniband CLRU. Since the DLRUs aredistributed throughout the whole frequency bands of the physicalchannel, user equipments allocated to the DLRUs must share pilotsallocated to the DRUs which are distributed throughout the wholefrequency bands. Consequently, if the DAS-MAP region is allocated to theDLRU region to which the CAS A-MAP region is allocated, the DAS userequipments must share pilots allocated to the DLRU. As a result, asdescribed with reference to FIG. 13, a problem that only two pilotpatterns must be used is generated. In a case in which controlinformation different for each antenna node proposed by the presentinvention is transmitted, therefore, a maximum of 2 different controlinformation can be transmitted. Consequently, it is preferable for theDAS-MAP region to be located at a Contiguous Resource Unit (CRU) or aDRU at which the A-MAP region is not present. For example, the DAS-MAPregion may be located at the DRU of the remaining frequency partitionexcept the primary frequency partition which is power-boosted when anFFR is applied. The base station processor 400 b may control the basestation transmitter 100 b to allocate the DAS-MAP region to the CRU orthe DRU at which the CAS A-MAP region is not present. Under control ofthe base station processor 400 b, the base station transmitter 100 b mayallocate a DAS-MAP to the CRU or the DRU at which the CAS A-MAP regionis not present.

Meanwhile, the base station may signal pilot configuration informationof the DAS-MAP region and/or MIMO transmission information of theDAS-MAP region to the user equipment. Information regarding the numberof pilots and information regarding pilot patterns may be signaled tothe user equipment as the pilot configuration information, and encodinginformation, precoding information, and information regarding the numberof multiplexed streams may be signaled to the user equipment as the MIMOtransmission information. MCS level information, code rate information,modulation order information, and burst size information may be utilizedas the encoding information. The pilot configuration information and/orthe DAS-MAP information may be transmitted to the user equipment throughan SFH, non-user specific A-MAP IE, or MAC message (for example, anAAI_SCD message or an AAI_DL_IM message). The SFH, non-user specificA-MAP IE, or MAC message may include one or more selected from amongposition information of the DAS-MAP region, size information of theDAS-MAP region, pilot configuration information of the DAS-MAP region,and MIMO transmission information. Alternatively, some or all selectedfrom among the position information of the DAS-MAP region, the sizeinformation of the DAS-MAP region, the pilot configuration informationof the DAS-MAP region, and the MIMO transmission information may benamed as individual IEs for DAS-MAPs and may be transmitted to the userequipment through the A-MAP region or the DAS-MAP region.

According to the embodiments of the present invention as describedabove, more than 2 pilot patterns may be used in the DAS-MAP region sothat other MIMO transmission technologies (for example, spacemultiplexing) except the SFBC can be used to transmit controlinformation. For example, in a case in which the pilot configurationinformation and the MIMO transmission information are transmitted to theuser equipment, the user equipment may find control information thereoffrom the DAS-MAP region using the pilot configuration information andthe MIMO transmission information. For example, in a case in whichantenna information is not clearly signaled, the user equipment may finda pilot, antenna, antenna node, and/or antenna group associated withcontrol information of the user equipment from the DAS-MAP region usingvarious pilot combinations based on the pilot configuration informationand may find control information of the user equipment in the DAS-MAPregion using a channel estimated through the pilot.

—DAS According to 3GPP LTE

As previously mentioned, each antenna transmits the same controlinformation on the control region according to the current 3GPP LTE.According to the regulations of the current 3GPP LTE, therefore, it isnot possible to transmit control information different for each antennanode.

If the regulations of the current 3GPP LTE are applied to a DAS standardwithout change, it is not possible to transmit a PDCCH different foreach antenna node from the current control region, e.g. first threesuccessive symbol sections of a subframe. Consequently, the presentinvention defines a control region (hereinafter, referred to as aDAS-PDCCH region) on which a PDCCH (hereinafter, referred to as aDAS-PDCCH) for a DAS user equipment is transmitted, which is differentfrom a control region (hereinafter, referred to as a CAS-PDCCH region)on which a PDCCH (hereinafter, referred to as a CAS-PDCCH) for a legacyuser equipment is transmitted.

According to the current 3GPP LTE, a PDCCH may be transmitted in firstthree symbols of a subframe. That is, a PDCCH may be allocated to firstthree symbols of a subframe. As previously mentioned, the number ofsymbols in which a PDCCH is transmitted may be changed depending uponthe number and/or size of PDCCHs to be transmitted. For example, in acase in which first three symbols are utilized as a CAS-PDCCH region,the base station transmits a CAS-PDCCH(s) for a legacy user equipment(s)in the first three symbols of a subframe through an antenna or allantennas. The base station transmits a DAS-PDCCH(s) to some of theremaining symbols except the three symbols. In this case, the basestation may transmit DAS-PDCCHs different for each antenna node. Forexample, the base station may transmit the DAS-PDCCH(s) from apredetermined number of symbols following the front symbols at which theCAS-PDCCH region is located or may transmit the DAS-PDCCH(s) on at leastone of PRBs in a PDSCH region of the subframe.

Meanwhile, the base station may signal reference signal configurationinformation of the DAS-PDCCH region and/or MIMO transmission informationof the DAS-PDCCH region to the user equipment. Information regarding thenumber of reference signals and information regarding reference signalpatterns may be signaled to the user equipment as the reference signalconfiguration information, and encoding information, precodinginformation, and information regarding the number of multiplexed streamsmay be signaled to the user equipment as the MIMO transmissioninformation. MCS level information, code rate information, modulationorder information, and burst size information may be utilized as theencoding information.

For example, referring to FIGS. 8 and 9, ANT1 and ANT2 transmit aDAS-PDCCH regarding UE1 and a DAS-PDCCH regarding UE2 on the DAS-PDCCHregion, and ANT3 and ANT4 transmit a DAS-PDCCH regarding UE3 and aDAS-PDCCH regarding UE2 on the DAS-PDCCH region. Also, ANT1 to ANT 4 maytransmit CAS-PDCCHs regarding legacy user equipments from theconventional control region.

The base station processor 400 b controls the transmitter 100 b toallocate a CAS-PDCCH to the conventional control region to which theconventional PDCCH in the subframe can be allocated and controls thetransmitter 100 b to allocate a DAS-PDCCH to the DAS-PDCCH region. Undercontrol of the base station processor 400 b, the resource element mapper305 may allocated the DAS-PDCCH to the DAS-PDCCH region.

Each legacy user equipment may blind decode CAS-PDCCHs transmitted onthe conventional control region to detect a PDCCH thereof. Each DAS userequipment may blind decode CAS-PDCCHs transmitted on the DAS-PDCCHregion to detect a PDCCH thereof.

The processor 400 a of the DAS user equipment may blind decode a set ofDAS-PDCCH candidates in the DAS-PDCCH region to detect a PDCCH thereof.The processor 400 a may demask the DAS-PDCCH candidates using anidentifier thereof to recognize a PDCCH having no CRC error as a PDCCHthereof and may control the receiver 300 a to receive and/or decode datathereof transmitted on the data region using control informationtransmitted through the PDCCH.

Meanwhile, a new reference signal may be defined for each number of datastreams to which DAS-PDCCHs are transmitted and may be transmittedseparately with CRSs. The user equipment may use the new referencesignal to estimate channel status, to demodulate a data stream thereof,which is one of a plurality of data streams transmitted by the basestation, or to detect a data stream including control information ordata thereof from among a plurality of data streams transmitted by thebase station. In a case in which a CRS is not defined and transmittedfor each antenna combination but a new reference signal is defined andtransmitted for each number of data streams, reference signals aredifferently defined according to the number of data streams that can besimultaneously transmitted, i.e. ranks, and therefore, it is possible toreduce overhead of reference signal transmission as compared with a casein which the CRS is used. Also, such a reference signal is transmittedafter the same precoder as the other data signals of the correspondingresource region being applied to the reference signal, and therefore, itis not necessary for the base station to inform a terminal of precoderinformation (PMI information). Such a reference signal, a referencesignal pattern of which is changed according to the precoder and thenumber of data streams is also referred to as a DeModulation ReferenceSignal (DMRS). A DMRS with respect to a data stream is transmitted onthe corresponding data stream, DMRSs on different data streams aredefined so as to be mutually orthogonal so that the DMRSs can be used todemodulate information transmitted through the data streams. In orderfor the base station to simultaneously transmit different DAS-PDCCHs tovarious user equipments through the same resource, therefore, it isadvantageous to transmit the DMRSs on the DAS-PDCCH region so that theuser equipments can demodulate the DAS-PDCCHs.

According to the current IEEE 802.16 and 3GPP LTE, a control channel maybe allocated and transmitted every subframe. That is, a CAS-PDCCH istransmitted in first three symbols every subframe, and a CAS A-MAP istransmitted on a DLRU in the primary frequency partition every subframe.In the above description, a case in which a control channel istransmitted every subframe even in the DAS system was assumed, and anembodiment for transmitting a DAS-PDCCH or DAS-MAP together with aCAS-PDCCH or CAS A-MAP on a resource region different from a CAS-PDCCHregion or CAS A-MAP region every subframe was described.

In a case in which it is defined that a user equipment supported foreach subframe is differently set in the DAS system, however, a DAScontrol channel may be allocated to a region to which the conventionalCAS control channel is allocated. For example, in a case in which a basestation wishes to transmit a PDCCH, the base station may transmit aDAS-PDCCH in the first three symbols of a DAS subframe and may transmita CAS-PDCCH in the first three symbols of a CAS subframe. On the otherhand, in a case in which the base station wishes to transmit an A-MAP,the base station may transmit DAS-MAP IEs on the primary frequencypartition of the DAS subframe and may transmit CAS A-MAP IEs on theprimary frequency partition of the CAS subframe. Informationindentifying which subframe is a DAS subframe or a CAS subframe may besignaled to a user equipment through a PCH, SFH, PBSH, SIB, etc.

The above embodiments described to solve compatibility with legacy userequipments are provided to achieve the proposal of the present inventionto transmit different control information on a predetermined resourceregion for each antenna or antenna node under a premise that restrictionconditions of control channel transmission required by the current IEEE802.16 and 3GPP LTE are effective. If such restriction conditions arenot present in transmission of control information, it is possible totransmit different control information on a predetermined resourceregion for each antenna or antenna node without newly prescribing aDAS-MAP and a DAS-PDCCH.

In IEEE 802.16, if it is not necessary to transmit an A-MAP in the formof two data streams unlike conditions required by the current IEEE802.16m, a base station may configure various A-MAP IEs into more than 2data streams and may transmit pilots according to pilot patterns basedon the number of the data streams.

FIG. 15 is a view showing an example of pilot patterns for four datastream transmission in IEEE 802.16m. For example, referring to FIG. 15,if A-MAP IEs are transmitted after being configured into four datastreams, the base station groups antennas into four antenna groups in anA-MAP region using an antenna grouping method and transmits pilots usingfour pilot patterns. Each antenna group may simultaneously transmitA-MAP information to be transmitted by the corresponding antenna groupusing a corresponding one of the four pilot patterns.

In 3GPP LTE, if space multiplexing is applied to transmission of aPDCCH, the base station may transmit different control information on apredetermined control region for each antenna node. Control informationregarding a legacy user equipment or a DAS user equipment moving at highspeed may be transmitted through all antennas. In this case, the DASuser equipment may receive or acquire control information thereof usinga CRS of an antenna or antenna node allocated to the control informationthereof. The legacy user equipment may estimate channel status betweenantenna nodes of the base station and the legacy user equipment usingall CRSs and may receive only control information thereof from controlinformation transmitted by the base station based thereupon, or mayacquire control information thereof from the received controlinformation through blind decoding. The DAS user equipment moving athigh speed may use all CRSs to receive control information thereof or toacquire control information thereof.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. For example, those skilledin the art may use each construction described in the above embodimentsin combination with each other. Accordingly, the invention should not belimited to the specific embodiments described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

INDUSTRIAL APPLICABILITY

The present invention can be used in a multi-node system providing acommunication service to a user equipment or a user equipment groupthrough a plurality of nodes.

1. A method of transmitting control information at a base station in animproved system comprising a plurality of antennas, the methodcomprising: transmitting first control information for one or morelegacy user equipments not supporting communication according to theimproved system on a first resource region; and transmitting secondcontrol information for one or more improved user equipments supportingcommunication according to the improved system on a second resourceregion different from the first resource region.
 2. The method accordingto claim 1, wherein the step of transmitting the first controlinformation comprises transmitting the first control information on thefirst resource region through each of the plurality of antennas, and thestep of transmitting the second control information comprisestransmitting the second control information on the second resourceregion through some or all of the plurality of antennas.
 3. The methodaccording to claim 2, wherein the step of transmitting the secondcontrol information comprises: transmitting control information for afirst user equipment group including one or more improved userequipments on the second resource region through a first antenna groupincluding one or more antennas from among the plurality of antennas; andtransmitting control information for a second user equipment groupincluding one or more improved user equipments, which is different fromthe first user equipment group, on the second resource region through asecond antenna group including one or more antennas from among theplurality of antennas.
 4. The method according to claim 1, comprising:transmitting at least one of size information and position informationof the second resource region, and stream number information.
 5. Themethod according to claim 1, wherein the second control information isadvanced MAP (A-MAP) information or PDCCH information, and if the secondcontrol information is the A-MAP information, the second resource regionis located at a Contiguous Resource Unit (CRU) in a primary frequencypartition in which the first resource region is located or at aDistributed Resource Unit (DRU) in a frequency partition except theprimary frequency partition, and if the second control information isthe PDCCH information, the second resource region is located at apredetermined number of symbols following a symbol(s) of a subframe atwhich the first resource region is located or at one or more PRBs in aPDSCH region of the subframe.
 6. A base station for transmitting controlinformation in an improved system comprising a plurality of antennas,the base station comprising: at least one of the plurality of antennas;and a processor configured to control the plurality of antennas totransmit first control information for one or more legacy userequipments not supporting communication according to the improved systemon a first resource region and to control the plurality of antennas totransmit second control information for one or more improved userequipments supporting communication according to the improved system ona second resource region different from the first resource region. 7.The base station according to claim 6, wherein the processor controlsthe plurality of antennas to transmit the first control information onthe first resource region through each of the plurality of antennas andto transmit the second control information on the second resource regionthrough some or all of the plurality of antennas.
 8. The base stationaccording to claim 7, wherein the processor controls a first antennagroup including one or more antennas from among the plurality ofantennas to transmit control information for a first user equipmentgroup including one or more improved user equipments on the secondresource region and controls a second antenna group including one ormore antennas from among the plurality of antennas to transmit controlinformation for a second user equipment group for one or more improveduser equipments, which is different from the first user equipment group,on the second resource region.
 9. The base station according to claim 6,wherein the processor is configured to control the plurality of antennasto transmit at least one of size information and position information ofthe second resource region, and stream number information.
 10. The basestation according to claim 6, wherein the second control information isadvanced MAP (A-MAP) information or PDCCH information, and if the secondcontrol information is the A-MAP information, the processor disposes thesecond resource region at a Contiguous Resource Unit (CRU) in a primaryfrequency partition in which the first resource region is located or ata Distributed Resource Unit (DRU) in a frequency partition except theprimary frequency partition, and if the second control information isthe PDCCH information, the processor disposes the second resource regionat a predetermined number of symbols following a symbol(s) of a subframeat which the first resource region is located or at one or more PRBs ina PDSCH region of the subframe.
 11. A method of receiving controlinformation at a user equipment in an improved system comprising aplurality of antennas, the method comprising: receiving second controlinformation for one or more improved user equipments including the userequipment, which support communication according to the improved system,from at least one of the plurality of antennas, wherein the secondcontrol information is received on a second resource region differentfrom a first resource region, on which first control information for oneor more legacy user equipments not supporting communication according tothe improved system is received.
 12. The method according to claim 11,wherein the first control information is received on the first resourceregion through each of the plurality of antennas and on the secondresource region through some or all of the plurality of antennas. 13.The method according to claim 12, wherein the step of receiving thesecond control information comprises: receiving control information fora first user equipment group including one or more improved userequipments on the second resource region through a first antenna groupincluding one or more antennas from among the plurality of antennas; andreceiving control information for a second user equipment groupincluding one or more improved user equipments, which is different fromthe first user equipment group, on the second resource region through asecond antenna group including one or more antennas from among theplurality of antennas.
 14. The method according to claim 11, comprising:receiving at least one of size information and position information ofthe second resource region, and stream number information.
 15. Themethod according to claim 11, wherein the second control information isadvanced MAP (A-MAP) information or PDCCH information, and if the secondcontrol information is the A-MAP information, the second resource regionis located at a Contiguous Resource Unit (CRU) in a primary frequencypartition in which the first resource region is located or at aDistributed Resource Unit (DRU) in a frequency partition except theprimary frequency partition, and if the second control information isthe PDCCH information, the second resource region is located at apredetermined number of symbols following a symbol(s) of a subframe atwhich the first resource region is located or at one or more PRBs in aPDSCH region of the subframe.
 16. A user equipment for receiving controlinformation in an improved system comprising a plurality of antennas,the user equipment comprising: a receiver configured to receive signalstransmitted from the plurality of antennas; and a processor configure tocontrol the receiver to receive second control information for one ormore improved user equipments including the user equipment, whichsupport communication according to the improved system, from at leastone of the plurality of antennas, wherein the processor detects thesecond control information on a second resource region different from afirst resource region, on which first control information for one ormore legacy user equipments not supporting communication according tothe improved system is received.
 17. The user equipment according toclaim 16, wherein the first control information is received on the firstresource region through each of the plurality of antennas and on thesecond resource region through some or all of the plurality of antennas.18. The user equipment according to claim 17, wherein, controlinformation for a first user equipment group including one or moreimproved user equipments is received on the second resource regionthrough a first antenna group including one or more antennas from amongthe plurality of antennas, and control information for a second userequipment group including one or more improved user equipments, which isdifferent from the first user equipment group, is received on the secondresource region through a second antenna group including one or moreantennas from among the plurality of antennas.
 19. The user equipmentaccording to claim 16, wherein the receiver receives at least one ofsize information and position information of the second resource region,and stream number information.
 20. The user equipment according to claim16, wherein the second control information is advanced MAP (A-MAP)information or PDCCH information, and if the second control informationis the A-MAP information, the second resource region is located at aContiguous Resource Unit (CRU) in a primary frequency partition in whichthe first resource region is located or at a Distributed Resource Unit(DRU) in a frequency partition except the primary frequency partition,and if the second control information is the PDCCH information, thesecond resource region is located at a predetermined number of symbolsfollowing a symbol(s) of a subframe at which the first resource regionis located or at one or more PRBs in a PDSCH region of the subframe.21-40. (canceled)